[Boatanchors] RF Distribution Amplifier

[WBob]

20 years ago I designed and built a distribution amplifier for 10-500 MHz. I used a 
single transistor, designed for cable TV that had a very low noise figure, but a very 
high current capability (1 amp I recall). I used an emitter-follower configuration 
with all 20 receivers fed with 50 ohm series resistors for isolation in parallel on 
the output and the antennas on the input. No tuning.

Using the same concept with the 807, set up a bias point that will give an output 
impedance of 5 ohms or less as a cathode follower and see what happens. Note that the 
output impedance of the cathode follower is not just the value of the cathode 
resistor, but much less.. go find an equation somewhere.

WBob

Barry Williams wrote:
> During WWII the british built radio intercept stations with a pair of
> rhombics, one for 3-9 Mhz. and the other for 9-27 Mhz.  These fed up to 24
> HRO receivers (also a lesser number of AR-88s and SX-28s).  In the
> references I have, there is mention of a distribution amplifier.  I asked
> one of the fellows who worked on them and he remembered that they were not
> tuned and used type 807 "valves".  I wanted to build a similar distribution
> amplifier for use with my HROs (a dozen or so).  Does anyone have a circuit
> for something like this?  The input
> impedence of the HRO was on the order or 300-600 ohms, although they seem to
> work with a 50 ohm input pretty well.
> 
> I don't think the distribution amp had very much gain ( a couple of db or
> less), so it was basically an input circuit matched for the rhombics and
> capable of driving an impedence as low as 15 or so ohms, or as high as 300
> ohms without much change in gain.
> 
> Thanks,
> Barry
> KD5VC
> 
> 
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