[Milsurplus] RE2/ARC5

[Mark K3MSB]

Hi Charlie

I have a new, probably never used,  BC-442-A Relay unit.

I measure 5 mA FS meter deflection with an internal meter resistance of
0.033 ohms.

These were measured by the usual means of a series resistance to give FS
deflection then a shunt to give half-scale deflection.

Across the meter leads of the thermocouple, I measure 1 ohm (meter
disconnected).
Across the other leads I measure about 0.7 ohms (wires also disconnected).
There lead resistances were subtracted out to give the above two
measurements.

Remember, the meter face reads Antenna Current Indicator -- there are no
units given.

As mentioned in other posts, at home I go through a 4:1 UNUN then through
an air variable series capacitor (an old HT-37 cap with some rotors
removed...) to get to 50 ohms to feed my home antennas.

Sometimes I see my BC-442 hit '2", other times it just budges a little, yet
my wattmeter shows 40 to 50 W out.  I think the current distribution
depends upon what antenna you are using and the matching network.

LIke others have said, one can ignore the relay meter reading when you have
a wattmeter in line further downstream.

As posted a few weeks ago, I experimented with a 45 foot random wire
antenna as that is what the B-24 used, but I did not have a counterpoise (I
didn't think about the fuselage being the counterpoise.....).
I plan to recreate that later this month with an insulated counterpoise and
see if that has any impact on the relay meter movement.

I hope this helps.

73 Mark K3MSB





On Fri, Jun 13, 2025 at 3:46 PM Charlie L. <mjcal79 at gmail.com> wrote:

> I have 2 RE2 antenna relay/RF ammeters, both meters seem inop.  I ohmed
> out the thermocouple free of external connections and are identical.  The
> meters have continuity, but with a Simpson 260 on RX1, only a flicker of
> movement.  I have a note that says these are 6MA movements, guessing that
> is DC out of the thermocouple not RF.  My TCS gear, when tuned up to 50
> ohms gives an amp reading coincident with RF out,  I would have expected
> these meters to do the same.  I get 50 watts out of a BC696A into 50 ohms,
> using the RE2 and the 50PF series cap in the back of it to feed 50 ohm
> coax, so I hoped to see 1 amp, but got nothing.  I also tried making a
> resistive load of 10 ohms to simulate a normal aircraft ant load of between
> 5-15 ohms, and still no meter reading.  What is the secret to this RF
> ammeter if it is not broken?
>
> Charlie in NC
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