[ARC5] US Vs German Tank Comm

[Neil]

> The Oxford Companion to WWII says that the Germans used the Fu5SE10 set in 
> armored vehicles, operating on a frequency of 27.2 to 33.3 MHZ. 
> Transmitter output power was 10 watts.
>
> Contrast this with the SCR-608 and 628, which used 27 to 38.9 MHZ with a 
> transmitter output power of 20 watts.
>
> So it is very possible that the American radios jammed German tank 
> communications, using FM radios that operated at twice the German output 
> power - and no doubt employing a lot more of them as well.
>

Actually, FM is jammed more effectively than AM is.
An AM signal can still be readable with a strong heterodyne present,
and sometimes even with heavy modulation present.
But a strong jamming carrier will *completely* silence an FM signal
due to the capture effect, and it needs to be only a few dB stronger
than the wanted signal.
I doubt the 2:1 power ratio you quote would make any significant
difference in the AM vs. FM jamming susceptibility issue. Much more
depends on other factors such as the transmitter-antenna impedance
match, propagation, terrain, receiver design, etc.

When considering the effectiveness of WWII radios, many fail to
appreciate that the philosophy for military radios is totally different
from that in amateur service. If the military radio has a short range,
that is not necessarily to its detriment but may be in keeping with its
design specification that it will be used to communicate with friendly
forces in the immediate area only, and greater range comes at the risk
of interception by the enemy or interference with your own forces
using the same frequencies somewhere totally remote. Having said
that, I'm at a loss to understand why frequencies in the vicinity of 30
MHz were used in some cases.

73 de Neil ZL1ANM