[Milsurplus] RE2/ARC5

[Mark K3MSB]

Mike

>> It still sounds unlikely to me.

Yep.....

To measure full scale current I used a Fluke 15B+ as well as a ME-29/U
meter.

My "technique" is the same one I've been using for years.....  series
resistance to get FS deflection then shut to get half scale deflection.
 Never had a problem with doing that.

73

Mark




On Mon, Jun 16, 2025 at 10:09 AM Mike Feher <n4fs at eozinc.com> wrote:

> Mark –
>
>
>
> It still sounds unlikely to me. Did you try to measure the total current
> using a current probe or another milliamp meter in series, like 10 MA full
> scale? I recently measured the internal resistance of a 0 to 1 ma meter
> using a bridge/Kelvin technique to minimize the current, and measured
> around 340 ohms. 73 – Mike
>
>
>
> Mike B. Feher, N4FS
>
> 89 Arnold Blvd.
>
> Howell NJ 07731
>
> 908-902-3831
>
>
>
> *From:* milsurplus-bounces at mailman.qth.net <
> milsurplus-bounces at mailman.qth.net> *On Behalf Of *Mark K3MSB
> *Sent:* Monday, June 16, 2025 9:53 AM
> *To:* Mike Feher <n4fs at eozinc.com>
> *Cc:* Charlie L. <mjcal79 at gmail.com>; milsurplus at mailman.qth.net
> *Subject:* Re: [Milsurplus] RE2/ARC5
>
>
>
> Hi Everyone.
>
>
>
> My apologies for not replying sooner.... Hamfest yesterday as well as
> Father's Day activities.
>
>
>
> There were no typos in my original email.   I was just as surprised at the
> internal resistance value as you were.
>
>
>
> This morning I performed the same measurements on a second relay unit.....
>
>
>
> Again, 5 mA full scale deflection.
>
>
>
> On the 2nd unit, I could get the FS reading to go half scale if I SHORTED
> the meter leads with a twenty inch alligator clip jumper....  this is
> repeatable with different sets of alligator clips.
>
>
>
> For the 1st unit (original email)...   I used three 0.1 ohm resistors in
> parallel as a shunt to give me the reported 0.033 ohm value.
>
>
>
> For the 2nd unit (tested this morning)....   four 0.1 ohm resistors in
> parallel as a shunt did not even give half scale deflection.
>
>
>
> I don't know what the resistance of the alligator clip jumper is, but it
> (obviously) has to be low.
>
>
>
> Just for fun,  I directly shorted the meter leads together (no jumper).
>  The meter went from FS to zero.
>
>
>
> What this is telling me is that the internal resistance of the relay meter
> is very low,  much lower than I expected.
>
>
>
> 73 Mark K3MSB
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
> On Sat, Jun 14, 2025 at 8:42 PM Mike Feher <n4fs at eozinc.com> wrote:
>
> Mark –
>
>
>
> I must have misunderstood what you said. The way I read it is that when
> the meter read 5 ma you measured 0.033 ohms. That comes out to 165
> microvolts for full scale. Just does not seem right. 73 – Mike
>
>
>
> Mike B. Feher, N4FS
>
> 89 Arnold Blvd.
>
> Howell NJ 07731
>
> 908-902-3831
>
>
>
> *From:* milsurplus-bounces at mailman.qth.net <
> milsurplus-bounces at mailman.qth.net> *On Behalf Of *Mark K3MSB
> *Sent:* Saturday, June 14, 2025 7:25 PM
> *To:* Charlie L. <mjcal79 at gmail.com>
> *Cc:* milsurplus at mailman.qth.net
> *Subject:* Re: [Milsurplus] RE2/ARC5
>
>
>
> 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
>
>
>
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