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

[Mark K3MSB]

Thanks for the replies guys -- way too many to answer at this hour....

Using scale drawings of the aircraft, I estimated the length of the antenna
from where it exits the fuselage to the top of the vertical stabilizer to
be about 34 feet.

The Antenna relay is on the opposite side of the fuselage from the exit
point, and the wire curves around the top of the fuselage before it exits
the fuselage.

Considering  the width of the fuselage, I added 8 feet for a total length
of 45 feet (antenna relay to vertical stabilizer).

Someone mentioned a book on B-24 radios -- I'm using "Service and
Instruction Radio B-24D Airplane, Consolidated Aircraft Corporation, San
Diego CA"  dated Nov 1, 1942.

I did consider the capacitive interaction between the antenna and plane,
but due to the distance to the vertical fin, I discounted it -- perhaps
incorrectly.

73 Mark K3MSB




On Mon, Jun 2, 2025 at 1:05 PM <scottjohnson1 at cox.net> wrote:

> I am guessing the difference is you don’t have a big aluminum counterpoise
> underneath your long wire (the fuselage). You may need more shunt
> capacitance.
>
>
>
> Scott W7SVJ
>
>
>
> *From:* arc5-bounces at mailman.qth.net <arc5-bounces at mailman.qth.net> *On
> Behalf Of *Mark K3MSB
> *Sent:* Monday, June 2, 2025 9:51 AM
> *To:* ARC5 <arc5 at mailman.qth.net>; mrcg at mailman.qth.net; List Milsurplus <
> milsurplus at mailman.qth.net>
> *Subject:* [ARC5] SCR-274N with B-24 Antenna
>
>
>
> 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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