Re: {Collins} 30L-1 / 20.5' Cable



Bill,

this matter came up already years ago. That time some person did some
intermod research depending on the length of the cable between transmitter
and 30L-1. He could not find any impact of cable length to overal
Intermodulation.

The time the 30L-1 was developped nobody had something like an antenna
analyzer. So in almost all cases the amplifier was matched to an antenna
impedance AROUND 50 ohms with the Collins filter. Minimum intermod is only
depending on the correct load impedance the tubes will see and this
impedance is always correct, if you manage to adjust your PI filter to a
correct conjugate match to your antenna. To accomplish this the SWR must
not at all be exactly 50 ohms but in the range of 1 to about 2...3.

Vy 73, Uli, DK4SX

2014-11-11 18:01 GMT+01:00 Bill Carns <wcarns@xxxxxxxxxxxxx>:

> Carl, That all will work, but you would be better served to re-dip the
> 30L-1
> as a final step. You have a lot of variables going there. The piece that
> you
> want to keep the happiest is the 30L-1 for optimum minimum IMD. What I do
> under such circumstances is to preset my tuner so that it is getting the
> G5RV as close to 50 ohms as possible and I do that with an antenna
> analyzer.
> Then, I tune the 30L-1.
>
> Regards,
>
> Bill
>
>
> -----Original Message-----
> From: Collins [mailto:collins-bounces+wcarns=austin.rr.com@xxxxxxxxxxxxx]
> On
> Behalf Of carl domanico
> Sent: Tuesday, November 11, 2014 8:07 AM
> To: collins@xxxxxxxxxxxxx
> Subject: {Collins} 30L-1 / 20.5' Cable
>
> OK thanks everyone for your input.so basically since i did get some varying
> suggestions on this matter it looks like the final outcome is that for all
> practical purposes.either length will work fine.as I mentioned I have used
> the 20.5' on my first 30L-1 some 20 + years ago and have the a 5' length on
> my second 30L-1 and both seem to function fine.so I guess I will just leave
> it that way !
> I use a G5RV antenna at this point..so I tune the exciter into my dummy
> load..then drive the amp .and tune that into my dummy load..then adjust my
> Palstar Tuner for minimum SWR at the frequency of operation..seems to work
> ok ! i was just curious about that 20.5' length It seems to work fine
> either
> way.so now I am useing the 5 ' length...
>
> Thanks a lot everyone..so it is not a critical matter.and seems to work
> fine
> weather I use the longer length or shorter length, just wanted input on
> that
> since it seemed to be a grey area..
>
> Thanks
> Carl
> WB2PVY
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