[TowerTalk] Re: Coax Discussions

[Peter Forbes]

The thread on coaxial losses at 28mhz has been interesting.

For those who feel that the "best" noise figure is necessary, you might try
the following:


Design and build a mast head receiving preamplifier that will switch the
1500 watt (less line losses) power that contesters are want to use.

The following points need to be considered.

(1) The gain does not need to be excessive, just the lowest NF you can get 

(2) You need to have relays that will switch effectively without introducing
transients

(3) You need static electricity protection, that will not just overload the
preamp when Joe CBer fires up on 27mhz down the road
(4) You need to be broadbanded to cover both CW and SSB 

(5) You will need to consider RF switching (with suitable delay) or hard
switching from the linear control circuits (the sequencing needs to be
effective)

(6) Consider using a nuvistor instead of solid state, so that static
protection is not as stringent.


Finally for the contester who wants every last dB, when you have designed,
built and successfully deployed such a device, put your mind to mast head
linear amplifiers.  Why not an Alpha 87A on top of the tower?


Cheers

Peter  VK3QI 


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