This blog was created to share my projects, ideas, and experiences in amateur radio with other operators around the world who also enjoy this wonderful hobby.

Wednesday, August 1, 2012

75 Ohm Coaxial Cable as an Alternative to 50 Ohms

photo 1

Coaxial cables with 75 ohm impedance can be obtained at reasonable prices and sometimes free. They are most of the time used for Satellite, Cable TV and CCTV ( Closed Circuit TV) video applications. In the picture above and from top to bottom, RG-11U, RG-6 and RG-59. RG-11U and RG-6 are used by satellite and cable companies in signal distribution and home installations. The main problem using this type of cable in 50 ohm applications is not the impedance factor. Most of these coaxials utilize an aluminum braid (shield) with a metalized foil, most of the time the ratio between braid and foil is 40/60. That is , an aluminum braid with 40% shielding, and the foil completing the remaining 60% for a total of 100% shielding. Ordinary PL-259 type connectors can not be used with RG-11U or RG-6 because of the aluminum shield. Aluminum can't be soldered as easy as copper, for example. All 50 ohm coaxial cables used in amateur radio applications are 50 ohm impedance and the braid (shield) is either copper or tin plated wire mesh. I will show you how to install the regular F connectors to the different types of 75 ohm coax cable and utilize an F to PL-259 adapter to build a good quality but cheap transmission line.


photo2

There are a variety of "F" type connectors for 75 ohm coax cable. From left to right, Ideal, snap ring type, for RG-6 and RG-6 Quad Shield, available at Home Depot. Augat, Snap and Seal ,by Thomas and Betts and the ordinary crimp type for RG-59 and RG-6 (F-59 and F-56) . The snap and seal type, are superior to the ordinary hex crimp type "F' connectors, because they  offer a very tight connection and are virtually impossible to strip from the cable.Snap and seal connectors need a special crimping tool to install them on the cable, the regular F-59 and F-56 are crimped with an "hex" crimping tool like the one pictured above. RG-59 and some varieties of RG-6/U can be found with copper shield and in that case ordinary PL-259's with the appropriate reducer adapter can be soldered directly to the cable. Use the UG-175/U reducer adapter with RG-59 and the UG-176/U reducer with RG-6/U. You have to make sure that the shield is copper or tin plated. As a general rule , if regular rosin core 60/40 solder does not adhere to the braid, most probably, it is not copper or tin plated. In that case you need to use the "F" connector approach.


photo 3


The above photo shows the different types of crimping and wire stripping tools available to work on 75 and 50 ohm coaxial cables. The top one (blue handles) is the regular "hex" type crimping tool for F-59 and F-56 connectors. Use the F-59 with RG-59/U and the F-56 with RG-6/U. If the coaxial you are using is the quad shield type ( the one with two aluminum and foil shields), make sure the F-56 connector is suitable for both RG-6 and RG-6 Quad, otherwise the connector won't fit on the quad shielded coax. The crimping tool in the middle is the Augat crimping, tool for the Thomas and Betts Snap and Seal connectors. The red crimping tool is from a different manufacturer and will crimp most of the snap type connectors from different manufacturers.The other two remaining tools are coaxial wire stripping tools for RG-11/ RG-8 type coax and RG-58/ RG-59/ RG-8X or RG-6 coaxial cables

photo 4

The first step is to remove about 3/8" from the outer cover, shield and dielectric at the cable end. The coaxial wire stripping tool shown above is from Radio Shack and is a two step stripping tool. Use the outermost position to strip the cable tip and the inner position to strip the outer cover (second step) This tool will work on RG-58, RG-59, RG-8X and RG-6 coax cables. If a coaxial wire stripping tool is not available, use a sharp knife to remove the outer cover, braid and dielectric material (foam or polyethylene), be careful not to cut the center conductor. Other types of stripping tools have two blades, and will strip the coax in just a single step. The cable an the top is RG-6/U and the bottom  is RG-59/U.


photo 5

In this photo, both coaxial cables after removing the outer cover, using the innermost position on the two step Radio Shack type tool (second step). About 3/8" of the outer cover is removed, if using another method, be careful not to cut the shield wires.


photo 6

After the cables are properly stripped, fold the braid down on top of the outer coaxial cover. Top coaxial cable is RG-6/U and bottom is RG-59/U


photo 7

This is how the cables look with the F-59 and F-56 type connectors installed and ready for crimping. Remember that they are crimped using the "hex" type crimping tool.


photo 8

If using the snap and seal type of connector insert the plastic ring first into the cable , then insert the connector. When the center conductor is visible at the top of the connector, the cable and connector are ready for the crimping tool.


photo 9

Insert the coaxial cable end with the connector inside the crimping tool and press the tool lever. The plastic ring will compress inside the bottom of the connector, the top part of the connector will move to the left up to the compress line. Once the ring is fully inserted, remove the connector from the tool and verify  the center conductor is centered inside the threads. Sometimes, if the center conductor is not centered prior to the crimping process, the crimping tool piston can bend the center conductor. If this happens ,use  long nose pliers to re-shape the center conductor.


photo 10


In this photo, notice the piston of the crimping tool as the lever is manipulated. Thomas and Betts snap and seal connectors use a band of different color on the plastic ring to identify the type of cable the connector will fit. Orange band is for RG-59, blue band is for RG-6 and purple band is for RG-6 Quad.. Please make sure you are installing the correct type on your coaxial cable, otherwise the connector is not going to install properly or won't fit.

photo 11

The other crimping tool I have for the snap and seal type "F" connectors. The process is the same as with the Augat tool explained above.  There are RCA and BNC  type connectors for the different coaxial cables available utilizing the snap and seal principle. The greatest advantage is that you don't have to solder and it will save time when installing multiple connectors. If you don't have or don't want to invest in the crimping and stripping tools there are other alternatives in those cases. One is , using the cheaper F-59 or F-56 "F" type connectors, the other is the poor mans approach to installing the snap and seal types. Place the connector inside the open jaws of a large plier or , drill a small hole into a piece of wood to insert the tip of the center conductor and the connector facing with the threads down. Hit the ring with the open jaws of a second plier , until it is fully inserted into the body. Be careful not to strip or damage the coaxial's outer cover as you hit the ring.


photo 12


In this photo, observe the different colors of the Thomas and Betts connectors, the type of cable they will fit is indicated by the color band. In this example, the one to the left (blue) is for RG-6/U , the one to the right (purple) is for RG-6 Quad Shield.

photo 13

In this photo, notice the difference in diameter between the F-59( (left) and the F-56 (right) "hex" type "F" connectors. They can be found at very low prices and offer a cheap alternative to terminate your coaxial cables. During an emergency ,when no electric power is available, while operating from remote locations or just to experiment with a new antenna , 75 ohm coaxial cable represent a good alternative prior to investing in higher cost ,expensive 50 ohm coaxial cable. Most hybrid transceivers with a pi- network tuned circuit on the final amplifier stage will easily load into 75 ohm coax. Most modern transceivers have built in tuners capable of tuning with 75 ohm coax. A half wave dipole on free space or installed high above ground will exhibit and impedance close to 70 ohms, thus making the 75 ohm coaxial cable a very good option as a transmission line. For the purists, a matching transformer can be used to transform the 75 ohm line to 50 ohms. On the other hand RG-6/U coax has a power handling capability very close to RG-213 type coax and very little loss. It can handle more power than RG-58, RG-59, RG-8X and even some types of RG-8's. The following table from VK1OD ,will show the power handling capability of the different types of popular coaxial cables.


photo 14

Once the "F" type connectors are installed , PL-259 to female "F" connector adapters can be used to easily convert the cable assembly. The adapters are also available in other configurations, BNC to "F", SO-239 to "F" , etc. If the cable assembly is going to be used outside, remember to protect the "F" connector and the adapter with heat shrink tubing or good quality electrical tape. I have used this type of coaxial assemblies with adapters with 500 watts of RF power in the HF bands without problems.


photo 15

Remember to tighten the "F" connector to the adapter firmly before protecting the connector , in case an outdoor application is needed. 75 ohm coaxial assemblies are also a very good option with receiving antennas and for the higher frequencies on scanner antennas.


photo 16

In this photo , a closer view of the completed "F" connector and adapter termination on RG-6/U coaxial cable. Another advantage is that a single length of 75 ohm coaxial cable, with "F" connectors on both ends, is very easy to convert to another type of cable assembly , just by changing the adapters.


photo 17

In this photo, the RG-11/U, 75 ohm  coaxial cable used in CATV distribution in some countries and the Augat cable stripping tool. This coax stripping tool will prepare the end of RG-11/U and RG-8/U in just one step for the connector installation. Two blades are utilized, one will strip the center conductor and the other will remove the bottom  outer coaxial cover.


photo 18

The RG-11/U as it looks after preparing the cable for the installation of the "F" connector. In this case the Tru-Spec crimping "F" type connector is used. Remember , most RG-11's like RG-6's use aluminum braid and foil ,thus soldering a PL-259 connector to them is not possible.This type of connector is crimped using a "hex" type crimping tool with a larger diameter. The center pin is pre assembled into the connector, there is no need to solder or crimp a center pin , like on other types of "F" connectors for RG-11.


photo 19

The RG-11/U coaxial cable after the "F" type connector is installed. It is a very fast and good quality termination for RG-11/U coaxial cable.



photo 20
The RG-11/U cable end with the installed "F" type connector and PL-259 to "F" female adapter. Remember , tighten the connector to the adapter firmly, and protect the assembly with heat shrink tubing or good quality electrical tape if going to be used outside.



photo 21

Comparison of the two types of "hex" crimping tools.The upper tool is for RG-11/U or RG-8/U coax. The one at the bottom is for RG-6 or RG-59 type cables. I have used the Tru-Spec RG-11/U "F" connector in RG-8/U and RG-213/U with good results, when PL-259's are not at hand, or just to experiment with a new antenna.


photo 22
A closer view of the jaw on the "hex" crimping tool for RG-59 / RG-6 coax cable.



photo 23

A closer view of the jaw on the "hex" crimping tool for the RG-11/U coax cable.


photo 24

Another alternative to the 'F' type connectors with PL-259 adapters are the crimp type PL-259 connectors available for RG-58 and RG-59. They are installed in the same way as the "F" type connectors, but require a different type of crimping tool. The tip of the connector to the center conductor can be crimped also, but I prefer to solder the center conductor and crimp the shield.


photo 25

The Amphenol ,ratcheting, crimping tool for RG-58, RG-59, RG-214 and other types of coaxial cables. The tool is expensive, but if you happen to have one available, it is a very good alternative to assemble jumper cables or coaxial cable assemblies on the fly.


photo 26

The Amphenol, ratcheting, crimping tool in action  with a crimp type PL-259 on RG-59 coaxial cable. The RG-6U connector will also work on RG8-X. In order to install an "F" connector on stranded center conductor coaxial cables like RG-8X , the center conductor wires need to be soldered to prevent strands from separating when installing the adapter or inserting the connector. Be careful not to use excessive solder, just the right amount to keep the strands as a solid conductor.There are also crimp type connectors available for RG-8/U type coaxial, but they are hard to find especially good quality ones. I hope this information , cable preparation and connector installation will help others  make good use of available 75 ohm coaxial cable in their respective countries. Here in Puerto Rico, satellite and cable TV installers ,throw away coaxial cable reels ,when the length of the remaining coax is not long enough for a new installation. I have found discarded reels ,with sometimes more than 70- 80 feet of coax, perfect for a new antenna project or experiment, and best of all, free. Any comments or contributions to this information are welcome.Until the next blog entry, 73's

Sunday, July 22, 2012

Baofeng Speaker Microphone Compatibility

Photo 1
 The Baofeng speaker microphone was received this week. I tested compatibility with the UV-3R and then
with the BF-U3, UHF model. The speaker microphone has very good transmit and receive audio with the UV-3R as reported by amateur operators on various repeaters locally. No push to talk issues were observed during operation. The speaker microphone audio response is a little on the high side (bright) for my taste,but overall quality is acceptable. I prefer the UV-3R internal speaker response and quality, but the brighter pitch of the speaker microphone is an advantage when operating in noisy environments.



Photo 2
 During transmit, no PTT issues were observed with the speaker microphone. In this photo the UV-3R is shown transmitting in high power. The included earphone / mic supplied with the radio does not suffer from the RFI issue reported with some UV-3R's. It  keeps the radio in transmit when operating on high power in the VHF band. I found a video on YouTube from SP3PWJ, showing a modification ( adding a disc capacitor to the earphone / mic ) to cure the RFI issue. This only has been reported in some radios, and only when using the supplied earphone / mic. The video is in polish, but has captions in English.




Photo 3


The Baoefeng UV- 3R's speaker microphone configuration. When viewed in this position and from left to right, tip is speaker out, ring two is microphone input, ring one is PTT input and the sleeve is common/ ground. On this microphone, the impedance of  the speaker is around 8 ohms and the microphone element is 1,500 ohms. This was calculated by the dc resistance readings obtained with my DMM (digital multimeter). 


Photo 4

The same tests were performed with the BF-U3 UHF radio. According to suppliers in Hong Kong and China, speaker microphone operation is not possible with the BF-U3. I discovered that it works with the speaker microphone, but the audio is weak. When tested with the supplied earphone / mic, the audio is loud and clear. I measured the dc resistance of the earphone/mic and found that it is above 30 ohms. The BF-U3 speaker microphone jack impedance is designed for higher impedance and does not work with the 8 ohm impedance of the speaker microphone. Adjusting the volume had little effect on the received audio when using the speaker microphone. Transmit audio was not a problem with the speaker microphone, on air reports were as good as with the UV-3R.


Photo 5

The BF-U3 is shown transmitting on high power with the speaker microphone. No PTT issues were observed, even with the microphone cable in close proximity to the antenna. The transmitted audio quality is the same as with the UV-3R , as reported by tests performed on the air,with other amateurs via repeaters. The speaker microphone provided better audio quality than the supplied earphone / microphone.






Photo 6

The BF-U3 receiving with the speaker microphone. The received audio quality is acceptable but very weak. In conclusion, the reason for this difference in volume is, the impedance of the speaker microphone ( 8 ohms) when compared to the higher impedance (30 ohms) of the supplied earphone microphone. Some vendors are selling speaker microphones and they claim compatibility with the BF-U3. I have tested different microphones from different suppliers and the results have been similar. This speaker microphone was purchased on E-bay from Solid Radio in Hong Kong. They cost less than $15.00 including shipping. There are other more expensive ones, including waterproof  versions, but they cost more than the radio alone. The other UHF mini hand held from Baofeng, the BF-U8 also suffers from the same speaker microphone compatibility. I will keep the speaker microphone for use with my UV-3R's and will use the BF-U3 with its internal speaker or with the supplied earphone microphone. This information was added to my blog as a complement to the Baofeng UV-3R and BF-U3 reviews and observations published earlier. You may find a  very nice compilation of information and FAQ's for the UV-3R . Any questions or comments are welcomed via e-mail, as well as your tests and observations with  Baofeng radios.

Sunday, July 15, 2012

Baofeng BF-U3 UHF 16 Channel Mini Hand Held

photo 1
The Baofeng BF-U3 UHF 16 channel mini hand held is a two watt transceiver covering from 400 to 470 mhz. The size is similar to the popular UV-3R , uses the same battery and accessories but can not be programmed from the front panel. The BF-U3 can be set to low power operation (less than 1 watt) with the programming software. The programming cable and software is not included with the radio.

photo 2


The BF-U3 package includes, radio, UHF antenna (SMA male), 3.7 volt lithium ion battery ( 1500 ma.),
usb power supply charger, usb charging cable, battery charging cradle, belt clip, in ear type earphone /mic with ptt , user's manual and lanyard.

photo 3

The Baofeng BF-U3 mini hand held compared to the dual band model, UV-3R. The case is about the same size as the UV-3R but there are no front panel buttons , just the left side buttons and the channel selector knob on top.The antenna supplied with the BF-U3 is a single band antenna for the UHF band (400 - 470 mhz.)
The antenna supplied with the UV-3R is longer and is a dual band antenna. On older versions of the UV-3R , Baofeng supplied two antennas, one for VHF and one for UHF. The size of the UHF antenna on the older UV-3R's is about the same length as the one on the BF-U3. The performance of both antennas is the same.

photo 4    

 Front view of both radios. Notice that on the BF-U3 the speaker is located at  the top of the radio case, on the UV-3R the speaker is located at the bottom. Both radios use the same type of antenna connector ,the SMA male , any aftermarket SMA male antenna will fit. I have obtained good results on both models with the Nagoya NA-701 and the NA-773.


photo 5    
The back view of the BF-U3. The battery cover is the same as in the UV-3R and it also uses the same battery, a 3.7 volt, 1500 ma. lithium ion battery. The belt clip attaches to the back of the radio with one phillips screw. Battery contacts are located on the top of the metal chassis of the radio , the battery cover is secured in place with a sliding lock on the bottom of the case. Both , the cover and the battery can be removed with the belt clip attached to the radio.

photo 6

A close up view of the back . The metal chassis on the BF-U3 and the UV-3R are used as a heat sink for the final amplifier transistor, it is normal for the radio to heat up during  long transmissions on the two watt,  high power setting. The temperature never rises to an uncomfortable level , like in some five watt handhelds. When operated in the low power setting , it is warm most of the time, even in long transmissions.

photo 7   


Top view of the BF-U3. The antenna connector to the left, the built in torch led flashlight and the channel selector knob. On the dual band UV-3R the channel selector  knob is used for various functions, on the BF-U3, it is strictly for channel selection. When the knob is pulled, it selects your operating channel , from one to sixteen. When the knob is pushed , it locks the radio in the channel selected. When selecting channels ,the radio will announce the channel number in voice.  Below the channel knob is the TX / RX led, it glows green when receiving a signal , and red when transmitting.


photo 8



Right side view of the radio. The speaker microphone connection requires a four contact , 3.5mm plug. The radio includes the earphone/mic unit with push to talk switch. The programming cable is connected to the same jack. The cable is not included but it can be found on the internet from different suppliers , including E-bay. I ordered one some time ago from  409shop.com , to program the Baofeng UV-3R, it is the same cable the BF-U3 uses. . The programming software is different from the one used on the UV-3R and can be downloaded free from  409shop also . The lower connector is for the dc adapter charger. The battery can be charged using the supplied usb power supply (120 vac to 5 vdc) or from any available usb port with the supplied cable. It can be charged inside the radio or outside on the included charging cradle.


photo 9
Left side view of the radio.From top to bottom, ptt switch, M/L button and P/V button. The ptt is used to key the transceiver, when the external earphone/mic is used the radio's ptt switch still works.The M/L button is used to activate the torch led flashlight or to open the squelch (monitor). The P/V button is used to turn on or off the transceiver, it needs to be pressed for 2 seconds to either turn on or off. When turned on, the command is announced in voice thru the speaker, also it will announce in voice when powering off. The voice can be changed from chinese to english with the programming software. Pressing the P/V button rapidly will increase the volume in pre- determined steps. In order to set the volume to minimum , you need to cycle through  all the steps , reach maximum and then start from minimum again.



phone 10  


Rear view of the Baofeng BF-U3. Note the similarity with the dual band model ,the UV-3R.
The belt clip is attached to the radio with a single phillips screw. Both the battery cover and the battery can be removed from the radio with the clip installed. Be careful as the belt clip is thin plastic and is not spring loaded , it can break easily.


photo 11


Front view of the Baofeng BF-U3 while receiving a signal. The receive led will glow green. The metal on the front panel bottom is not real metal, it is a chrome plated sticker . The received audio is better than the audio on the UV-3R dual band model . This is related in part to the acoustics of the radio case and to the fact that the speaker is located on top of the front panel and not the bottom. Both models have 500 mw. audio output power.



photo 12

The Baofeng BF-U3 transmitting. The receive led changes from green to red, ptt is possible from the radio's ptt switch even when the earphone/mic is used. According to several vendors on the internet, the BF-U3 does not support speaker mike operation. With the included earphone /mic it works ok. I am still waiting for a mini speaker microphone I ordered last week to arrive for my UV-3R. I will test the speaker microphone once it is received with the BF-U3 in order to confirm this issue and will post or edit the information here. The power settings need to be programmed with software , either high or low, for each one of the sixteen channels and can not be changed from the radio.


photo 13   


Front view of the radio with the stock UHF antenna attached. Next to it , the Nagoya NA-773 dual band telescopic antenna. Reception is acceptable with the stock antenna, local repeaters can be accessed ok, at even the low power setting. I have found that  most mini handhelds like the Yaesu VX-3R , Icom IC-Q7A and the Baofeng's receive better when you are holding them in your hand. The human body by capacity couples to the radio , in most cases improving reception . When you place the radio on  your desk ,for example , sometimes reception is marginal. This is noticed mostly on the vhf frequencies and it is caused by the size of the radio.. The mini handhelds metal case is not large enough to provide an  adequate counterpoise on the vhf frequencies. I remember a company sometime ago ,selling a "rat's tail", it was a counterpoise wire that was attached to the antenna connector down the back of the hand held. It improved the reception and probably the transmission ,because it provided a quarter wave counterpoise radial to the transceiver. In real life or daily radio activity this is impractical , but it clearly explains the problem with the mini hand held's insufficient counterpoise. A longer antenna in most cases improves the reception , I have obtained good results on both radios, the BF-U3 and the UV-3R with the Nagoya NA-701 and the NA-773. The 773 is a dual band telescopic antenna and provides superior reception on both radios. The 701 is my choice for everyday operation as it is not too long. You have to compare and experiment with the different models available , your results may be different. In my tests the receive sensitivity of both radios is about the same, the BF-U3 when receiving fades more than the UV-3R ,but this has a lot to do with the short antenna. Using a longer antenna , improves the reception. RFI immunity on both radios is also the same on UHF. With the UV-3R operation on VHF near a computer,  monitor or  near a wireless router is impossible. This is related in part to the simple, zero IF, dsp design of both transceivers.

photo 14



This is the view of the BF-480 programming software on the computer screen. The program can be downloaded free from 409shop.com. It is not the same software used with the UV-3R so be careful. The first step is to configure the comm port for the usb cable to Baofeng mini plug. In my case I am using comm port number four. Start entering your receive and transmit frequencies ,starting with number, one until you reach channel number sixteen. Also enter the transmit pl tone or DCS , the transmit power (high or low),wide or narrow deviation and if you want to add the channel to the scan group. The busy lock out if left on, will prevent the radio from transmitting while a  channel is busy. If you don't want this feature, change the setting to off. Once you have all your information entered correctly, click on the program tab ,and in the pop out  window, click, write to radio. A progress bar will appear while the radio is programmed. Once programmed ,you can save your programming information in a file on the computer. If you want to see what is programmed, click on the program tab and select , read from radio. Programming all the channels is not needed , the radio will emit a constant beep when you select a channel that is not programmed.




photo 15



This is the view of the BF-480 programming software screen , with the programming I did on my Baofeng BF-U3. There are not many active repeaters in Puerto Rico that I am able to use with two watts from the capital (San Juan). I was able to test twelve repeaters that were  within range , programmed those frequencies and left four channels empty for future use. The software is very user friendly and the programming process can be completed in very little time, if you have the list of frequencies already organized. On the Baofeng UV-3R there are a total of 99 memory channels, it will take more time to program the complete set of memories on that radio. If you have any questions or comments regarding the Baofeng BF-U3 uhf mini radio or the UV-3R , subject of an earlier blog entry, please contact me via e-mail. I hope this information helps deciding which radio is a better option in your particular application and clarifies the programming process with the BF-480 software.





Wednesday, July 11, 2012

Dipole Antenna Construction Ideas

Step 1
The materials needed for the dipole antenna construction are shown above. We are going to use the dipole antenna center insulator built earlier. The other materials are, 26 feet of #12 or #14 stranded copper wire, two pieces of heat shrink tubing 1/4" diameter by 1- 1/4" long. The length of the wire sections is calculated using the formula ,468/F(MHz). Approximate wire lengths  for the popular Amateur Radio bands will be given at the end of the building process. The dipole we are about to build is for the 15 meter band. From the formula 468 divided by 21.0 mhz = 22.28 feet. Divide the result by 2 to get the lenght of each side of the dipole. The wires need to be longer to compensate for the connection loops and adjustments. Cut each side to 13'  to be safe.




Step 2
 Start by inserting one end of the copper wire thru the top of a crimping ferrule, then go thru the eyebolt, and back thru the bottom of the ferrule making a 2 inch loop. Move the ferrule as close to the eyebolt as possible, but don't crimp it. Crimping will be done later.



Step 3 
Insert a piece of heat shrink tubing thru the wire on the dipole center insulator. The length of the tubing is 1-1/4 " and the diameter is 1/4 ".




Step 4
 Now, strip about 1/2" from the insulation on the antenna wire and the center insulator wire. Apply 60/40
rosin core solder to both wires and wait for the solder to cool.



Step 5
 The next step is to insert each wire into the splice cap. It is a good idea to apply solder to the inside of the splice cap , this will make soldering  the wires easier. Apply solder to the splice cap and the wires . Do not crimp the splice cap over the wires because corrosion will damage the connection in little time, always use solder. This splice cap can take more than one wire so it is possible to build a two band or a three band dipole, with a single center insulator. Up to three antenna wires plus the center insulator wire will fit inside the copper splice cap. If #12 gauge wires are used it will only take two plus the center insulator wire. A larger diameter splice cap can be used if  # 12 wires are preferred for the construction.



Step 6
 Wait for the splice cap and the wires to cool and slide the heat shrink tubing until it covers evenly the splice
cap and the wires. Repeat the same steps on the other side of the antenna. It is a good idea to verify continuity of your connections with a VOM (volt ohm meter) or a DMM (digital multimeter) before applying
heat to shrink the tubing. Good quality electrical tape can be used instead of the shrink tubing as well as liquid tape (available at Home Depot) or silicone sealant.




Step 7
Now it is time to install the end insulators to each side of the dipole. The process is similar to the one explained for the center insulator ferrule installation. Do not crimp the ferrule on the dipole ends. This will be done at the end when you install and test the antenna with an antenna analyzer or SWR meter. The ends can be adjusted for minimum SWR by adjusting the length of the antenna wires. This is easily done on the dipole ends.
When the antenna is tuned for the operating frequency or frequencies, then you crimp both ferrules at the ends.The center insulator ferrules can be crimped after the previous steps are completed.



Step 8 
A close view of the crimp splice cap connectors used for the center insulator wire connections. The are made by Buchanan, the part number is 72400, the package contains ten pieces. They are available at  Home Depot for a few dollars. If the connectors are not available it is possible to solder both wire connections with a good quality 60/40 rosin core solder and then  protecting the connection with shrink tubing, electrical tape, silicone sealant or liquid tape. Remember, the idea of the splice cap is to fit more than one wire at a time, making it possible to build a two or three band dipole and at the same time protect the connection from the elements.


Step 9 
 The ferrules are made of aluminum, the internal diameter is 1'8". They will take #14 and #12 gauge copper wire. They look similar to a binocular ferrite core. They are available at Home Depot and other hardware stores. Four ferrules are required to complete the antenna, each package contains two ferrules. I have seen them  listed for sale on E-Bay also at fair prices.




Step 10 
 Bottom view of the ferrule package, the round barrels are not used. The ferrules are available in different internal diameters, so it is posible to build a lighter antenna for QRP, with #18 copper wire and a center insulator made with 1/2" PVC material and a BNC connector,  instead of 1" PVC material and a SO-239 connector. Also if larger diameter wire is needed, like #10 for example, a larger ferrule can be used to complete the antenna construction in the same way as with smaller diameter wire.



Step 11 
 A close up view of the aluminum ferrules. If bare copper wire is used for the antenna construction, like # 14 copper-weld, do not use the aluminum ferrules. Solder the wires from the center insulator directly to the dipole antenna wires with good quality 60/40 rosin core solder and protect the connection point with liquid tape or silicone sealant. If the ferrule is used with bare copper wire, a chemical reaction will take place between the dissimilar metals, destroying the connection in little time. Do not use any type of crimping terminal to make the connections, as the connection will deteriorate rapidly and a resistance will be created at the connection affecting your antenna performance.



Step 12
 This is how the center insulator looks with both dipole wires already soldered to it. If you haven't already checked for continuity, it is now the time to do it , before applying the shrink tubing to the splice caps.



Step 13
 Now, the shrink tubing pieces are in place. Use a heat gun, hair blower or matches to shrink the tubing. Be careful not to melt the wire insulation.


Step 14
 If a crimping tool is not available, use a large flat blade srewdriver to crimp the ferrules. Hit the ferrules with the screwdriver and a hammer along the center on both sides, until the ferrule is completely holding both wires. Do not hit to hard or you will nick or break the ferrule.


Step 15
The completed half wave dipole antenna. This one in particular is cut for the 15 meter band. Between twelve or thirteen feet of cable are used on each side of the antenna. Remember, do not crimp the ferrules at the end of the dipole until you install the antenna and adjust both sides, adding or subtracting to the wire at the ends. Use an antenna analyzer or SWR meter to adjust the dipole to the desired center frequency. Remember, making the antenna longer , lowers the resonant frequency and making it shorter, increases the frequency. The dipole is a balanced antenna, both sides must be equal in length, if you add wire to one end, add the same amount to the other and vice versa. When the SWR is set to an acceptable level, lower the ends of the dipole and crimp the ferrules. Surrounding objects, the height above ground and the antenna configuration ,(inverted vee, sloper, horizontal, vertical, etc.) will influence the size of the wire elements on your particular installation. That is why it is advised to always use one to two feet of extra wire on each end to tune the antenna. Don't let a long piece of wire hang from the dipole antenna ends as it will add to the total lenght of the antenna and fool your adjustments. Wrap the excess wire over the antenna wire backwards, when you are satisfied with the tuning, crimp the ferrules and cut the extra wire on both ends. From the half wave antenna formula 468/F(MHz) remember the result is the total wire length of the antenna, divide the result by two and add one feet of wire to aid in the tuning process. That said, you will need two 10' sections on 10 meters, two 13' sections on 15 meters, two 18' sections on 20 meters, two 35' sections on 40 meters or two 70' sections on 80 meters to build a half wave dipole antenna for your band or bands of choice. If you have any comments or questions about the dipole antenna construction process or need technical help with your particular application, please contact me via e-mail. I hope this information helps other amateurs take the challenge and build their own good quality half wave dipole antenna, saving money and learning at the same time.