[ARC5] Getting ARC5 and SCR-274N Txs on 40 m

[Mike Morrow]

Wayne wrote:

> Has anyone figured out which Command Set transmitters can be changed in
> frequency just by swapping out the MO coil?

I have a cross-reference for all the frequency-dependent A.R.C. part numbers used in all such sets from RAT to post-WWII A.R.C. Type 12 that I'll post as a pdf in a few weeks when I get some new computer gear.  In the meantime, here is a text excerpt for all of the transmitters:  (You may need to view in PLAIN TEXT for correct display of the table.)
                                    A.R.C. PART NUMBERS FOR
SYSTEM          FREQ (MHz)   T-53A (MO)     T-54A (PA)     L-52 (ANT)

ATA (CBY/CCT-)
52232           2.1-3.0      7988           7991           7992
52208           3.0-4.0      6029           7247           6033
52209           4.0-5.3      6030           7248           6034
52210           5.3-7.0      6031           7249           6035
52211           7.0-9.1      6032           7250           6035

SCR-274-N
BC-696-A        3.0-4.0      6029           7247           6033
BC-457-A        4.0-5.3      6030           7248           6034
BC-458-A        5.3-7.0      6031           7249           6035
BC-459-A        7.0-9.1      6032           7250           6035

AN/ARC-5
T-15            0.5-0.8      9214           9226           9271
T-16            0.8-1.3      9219           9231           7992
T-17            1.3-2.1      9223           9234           7992
T-18            2.1-3.0      7988           9291           7992
T-19            3.0-4.0      6029           9292           6033
T-20            4.0-5.3      6030           9293           6034
T-21            5.3-7.0      6031           9294           6035
T-22            7.0-9.1      6032           9295           6035

>From the above table it can be determined which specific component is used in each transmitter.  For any one system, only the antenna inductance may have been used in more than one transitter range.

Mike / KK5F


 
For example, can you take a 5.3 to 7 MHz set and 
just put in a 7MHz MO coil?  Or take a 4 to 5.3 MHZ transmitter 
and put in a MO coil suitable for 80M?   
 
Obviously there are other tuned circuits in the 
transmitter but do they have the range required to handle the MO?
 
And obviously you would need a new dial, but taking 
a circle of aluminum and making markings on it based on your frequency counter 
or a receiver with known calibration is an easy and quick swap out task.  
The idea is, of course to change the frequency of the less 
desirable transmitters without doing anything that would not be easily 
reversible.
 
The 4 to 5.3 MHZ transmitter I have in which I 
will be changing the MO coil to one for 7 MHZ already has everything 
but the MO coil and tuning cap stripped out, by the way.
 
Wayne
WB5WSV