Re: 75 ohm coax

Posted by Adrian-3 on Apr 01, 2020; 11:52pm
URL: http://elecraft.85.s1.nabble.com/75-ohm-coax-tp7659432p7659435.html

In old days hams fed 10:1 antennas with ladder line and did well.

Just keep feedline loss to a minimum. I feed my apex high delta loops
direct with a good toroid coax choke at feedpoint at bottom corner (low
impedance) near the shack.

Coax is short and lmr240, works great. I tested 2:1 & 4:1 baluns etc on
previous advice and the result was not as good as a good direct feed
with high impedance choke.

Look out for vk4tux on FT8.



On 2/4/20 9:32 am, Josh Fiden wrote:

> This all reminds me of the difference between when I was a young teen getting started as a ham vs now.
>
> As a kid I would put things together or throw em up. Only worried about it after it didn’t work. Nowadays, I plan & overthink things to death before getting anything accomplished. I prefer the old way.
>
> 73,
> Josh W6XU
>
> Sent from my mobile device
>
>> On Apr 1, 2020, at 4:20 PM, Frederick Dwight <[hidden email]> wrote:
>>
>> If you have 75 ohm coax, I would just try it.  If the Z of the antenna is in fact around 35 ohms, the Z at the shack end may be close to 35 ohms on some bands, but on others the Z will be transposed to well over 100 ohms with an SWR probably over 3 to one.  One of my dipoles has a SWR at the top of 75 meters of approximately 4:1, and I occasionally venture up there, but my K3S with internal tuner does not complain and quickly matches it to about 1:1.  Not ideal and this is not the way I usually build my antennas, but the loss is not too bad.  If you can build a unun with approximately a 1:2 ratio this should solve your problem.  If it does not cover all the way from 80 to 10 with low loss, I would not worry too
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