Topband: Receiver front end protector

[Joe Subich, W4TV]

> It provides full DC isolation at all times to prevent against static
> discharge problems, and works on the principle of saturable reactors.
> It does not clip - it simply saturates at a reasonable voltage on the
> receiver side, and goes to a low impedance on the antenna side.

Unless the transformers in the ICE unit are carefully controlled - and
it's impossible to tell what the impedance ratios are from the pictures
- the ICE196 will most certainly clip at (probably) 1.4V p-p (1V RMS).

Back in the 1980's Doc Sheller, W8RR - now SK - sold a passive front
end protector that also used clip diodes and a series lamp as fuse
device.  He found it necessary to increase the clipping threshold by
adding a resistor in series with the diodes and may have had to go
to two diodes in series (2V P-P) to prevent significant IMD with
resonant antennas.

It has been at least 20 years since I even looked at Doc's data so
much of this is from memory.  If there is serious interest in passive
antenna protection devices, contact me *direct* (w4tv at subich.com).
I will start assembling list of interested parties and see if there
is "critical mass" for a commercial product or products using passive
protection.

73,

    ... Joe, W4TV



On 10/17/2011 9:27 AM, Hal Kennedy wrote:
> The ICE 196 is IMHO the best front end protection that was in the
> market.  It's too bad they are not currently available.  It provides
> full DC isolation at all times to prevent against static discharge
> problems, and works on the principle of saturable reactors.  It does not
> clip - it simply saturates at a reasonable voltage on the receiver side,
> and goes to a low impedance on the antenna side.  It requires no
> voltage, no switching and you just leave it in-line forever.  Running
> SO2R I am always driving one of them deep into saturation and it does
> not re-radiate anything into the other receiver.
>
> I thought about offering them for sale.  Someone should.  I am getting
> too old and lazy I think.
>
> 73,
> Hal N4GG
>
>
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