Re: Coax recommendation

John Buckley

Hi Chris,
I've just purchased a Loop Antenna Amplifier ++ from you and so far have made a very basic loop. 
You mention LDF4-50 , well , I have some Cellflex LCF 12-50 which appears to be the RFS equivalent .
Can you suggest or point me to some designs for using it in a loop antenna build please.

John  2E1JBC

On Tue, 23 Aug 2022 at 21:15, Chris Moulding <chrism@...> wrote:
For HF receive use with the High Z, Loop and Beverage amplifiers the coax losses are relatively low even for long runs so other factors such as cost, lifetime or ease of installation become major factors.

Most of the amplifiers are set up for 50 ohm output but it's a simple resistor change during build to give the option of 50, 75 or 100 ohm output impedance.

In actual receiver use the mismatch between 50 and 75 ohm coax is barely noticeable so 75 ohm CCTV cable is a good option.

Our earlier active antennas used CAT5 ethernet cable using one pair as a 100 ohm transmission line, two pairs for DC power with one pair spare. We did manufacture a cross polarised active antenna that used the spare pair as an additional RF transmission line to go with the dual diversity SDR receiver we made some years ago.

The only reason we stopped selling antennas using CAT5 cable was that our professional customers didn't want to replace their existing coax cable runs with CAT5.

What do I use myself? Both at home and in the workshop I use coax cable runs of RG-58u with runs up to 25 m long. It"s mainly due to the ease of installation and the fact we always keep a drum of it in stock to make connecting cables.

By the way in my previous professional life designing and installing coverage enhancer systems for mobile phone networks we only ever used Andrews LDF 4-50 cable. This would be well over the top for HF receive use but it's great for making HF loops!




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