[ARC5] SCR-274N with B-24 Antenna

[J Mcvey]

 Ok,50 pf is a boatload of capacitive reactance!  so the max complex impedance extreme is 12-j820
I use 2 parallel 100 pf transmit caps (50pf) in series with  driving my 1:9 unun.into a dipole on my ARCs.  I get  50 watts.I use very little inductance in this configuration. You would need quite a bit  of inductance on a short wire antenna.I did have mine running this was , once upon a time...
Try playing with the series cap value.

    On Monday, June 2, 2025 at 06:08:06 PM EDT, hwhall--- via ARC5 <arc5 at mailman.qth.net> wrote:  
 
 You're setting this up outside & not from inside a fuselage? The capacitance between the fuselage & the antenna wire must've been an important part of the total antenna circuit. Operating a wire in essentially "free air" without nearby conductors (e.g., as a ham-style nonresonant length endfed) would probably require adjustments to the wire length used, or additional tuning beyond the range expected by the stock Command Set transmitter.

"A single antenna may be used for all transmitters providing it has characteristics at each operating frequency within the following limits:
(1) A reactance not greater than that of 50 micromicrofarads or of 4.5 microhenries.
(2) A resistance of up to 12 ohms."
--TO 08-10-50, Instruction Book for Operation and Maintenance of Radio Set SCR-274-N" Feb 15, 1943

Wayne
WB4OGM

On Monday, June 2, 2025 at 10:51:11 AM MDT, Mark K3MSB <mark.k3msb at gmail.com> wrote: 

Hi Guys

The estimated length for the Command Set antenna on a B-24 is about 45 feet taking into account the length inside the fuselage.

I cannot get this work with my command set on 3885.   No antenna current at all.   Dosen't matter if I use the 200 pF cap on the antenna relay unit.

I can use my 9:1 Balun and series capacitor, the output of which goes to an MFJ tuner connected to the 45 foot wire.  I'm getting about 30W out with low Ip.

Don't understand what I'm doing wrong with only the 45 foot wire.

I can certainly do it this way at the airwhow this week, but I'd rather not have the MFJ box in line.

73 Mark K3MSB
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