I came away from Contest University 2012 at Dayton with a mission to upgrade the coax connection to my Butternut HF2V 80/40/30 meter vertical. Frank Donovan, W3LPL, had conducted an excellent presentation on Coaxial Feed Lines for Competitive Contesting. He really went into the right connectors (always PL-259 Amphenol 82-1SP), the right coax (Heliax or Davis RF Bury Flex), the right soldering and taping for waterproofing, etc. It made a great deal of sense to me. So I resolved that my first project would be to tackle the feed line to the HF2V.

The feed line run to that antenna is relatively short, about 30 feet from the 1:1 isolation balun just below the feed into the ham shack. While at Dayton, with all my Radio Scouting responsibilities, I didn’t have a chance to look for any of the items in the flea market. But, I did have time at HamCom. Short story is that I couldn’t find any heliax nor the Amphenol connectors. I did find the connectors through Mouser. And, I did find the Davis RF Bury Flex coax on ebay at a cost of about $90 delivered for 100 feet from K1CRA’s store front. So this past week I spent some time in the marginally cooler evenings to dig up the old coax line and install the new one. Photos below of the installation.

The end result is an excellent feedline into the HF2V. Now I’ll need to consider something similar to the MA6V. Improving a contest station is a never ending task! Thanks Contest University for so many good ideas for improvements.The previous line was LMR-240 run in 1/2 inch PVC with silicone sealant at each end. When I pulled that line up, the water, despite limited rain, ran out of the PVC for quite some time. The new line is 1 inch PVC conduit with holes drilled in the bottom of the line to allow for drainage of condensation etc. It is also open at both ends, with steel wool squeezed in the ends to prevent critters from entered but allowing air into the line. The Davis RF Bury Flex cable is very sturdy and fits the UHF connectors without an adapter. I also followed Frank’s soldering technique which can be found here. It calls for soldering the shield directly to the outside of the PL-259 and covering it with electrical tape. Next is protecting the connectors from moisture using Scotch 103C and Scotch 33 tape. Also found the right tape on ebay at a good price.

Replacing the old cable and PVC with the new PVC conduit.
Replacing the old cable and PVC with the new PVC conduit.
Base of the HF2V with coax matching line for 30 meters.
Base of the HF2V with coax matching line for 30 meters.
Base of HF2V with 1:1 isolation balun and PVC conduit with Davis RF Bury Flex cable.
Base of HF2V with 1:1 isolation balun and PVC conduit with Davis RF Bury Flex cable.
The run along with house into the PVC conduit run to the HF2V.
The run along with house into the PVC conduit run to the HF2V.
The PVC conduit run near the house before covering with dirt.
The PVC conduit run near the house before covering with dirt.

 

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Jim-K5ND

Freelance writer and active Scouting volunteer. Retired publishing and communication executive who writes for fun and to finance his hobby, amateur radio.

4 COMMENTS

  1. It is hard to respect advice to use UHF connectors. Hams and CB’ers are the only people still using that ancient technology. No professional RF gear uses them.

    UHF connectors are inferior to N connectors in every way except ease of installation. UHF connectors are not constant impedance, are not weatherproof, and can handle far less power. The impedance mismatch doesn’t hurt you at HF, but why buy top-grade coax and put UHF connectors on it?

    Scotch 33+? Yep, learned to always use that stuff working at KTRU in Houston.

      • If you are using a bad design, at least use the best implementation of it. That would be Amphenol.

        The Amphenol specs show a much higher peak power for type N than for UHF. Type N connectors are rated for 1500V, UHF for 600V. And the lowly BNC? 500V.

        The impedance “bump” of a UHF connector does not usually cause noticeable problems at HF, but it is very bad at UHF. At 440 MHz, expect to lose 1dB for every UHF connector.

What do you think?