List - The same lamp was used by Drake in an option for the TR-7 and
R7s. Called RP-7. Was sold as a "receiver protector" in a small box
that was inserted in the coax before the receiver input.
If someone needs one of the lamps I have a couple.
Also have a small number of the hard to find PIN diodes used in the TR-7
series.
73 Bob W7AVK
On 10/16/2011 8:28 AM, Garey Barrell wrote:
As others have said, it's a protective 'fuse' for the receiver in the
TR-3/4 series transceivers.
It's a worthwhile addition because again, the TR-3/4 series is an
EXCELLENT 'SSB Transceiver for _Mobile_ operation'. It's marginal for
other uses, but for it's design goal, terrific!
Mobile use is WHY the bulb is necessary. You won't have an 18-wheeler
carrying a 2 kW CB transmitter pull up next to your home shack,
but.... Even a 200 W transmitter with it's vertical antenna only a
few feet away from yours can fry an input transformer.. I have seen
the bulb in a TR-4 show a good glow with another nearby 200 W
transmitter on a different antenna and band.
The #12 bulb is identical to the #47 bulb electrically, just with
shorter leads. They are readily available from the on-line bulb
dealers, and shouldn't be replaced with a piece of wire, especially if
operated mobile.
Obviously an open bulb or even corrosion on the leads can severely
impact receiver sensitivity, second only to that %%#%$ 'TCVR/RCVR'
slide switch on the left side!
73, Garey - K4OAH
St Charles, IL
.
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