Comm Equipment

[Matt308]

Current US National Airspace Regulations require use of Very High Freguency (VHF) Double Side Band - Amplitude Modulation (DSB-AM) comm equipment operating in the 117.975-138.00MHz band. While most of the world uses comm equipment utilizing 25kHz channel spacing, Europe uses 8.33kHz channel spacing for upper altitudes (flight levels).

The VHF band has migrated from 100kHz, to 50kHz, to 25kHz (and in then in Europe to 8,33kHz) channel spacing.

What spectrum (band and bandwidth) and channel spacing did WWII aircraft use in the European and Pacific theaters? Certainly this will include both VHF and HF bands.

Put your thinking caps on for this one.

 

[Matt308]

OUch. Not even a bite. Where are the commo geeks?

 

[FLYBOYJ]

Just font this one...

It seems the US used 2 -12 mhz. Heres a site I had packed away.

WB6FZH Classic Military Radio- Boatanchors Mil-Radio Operating Historical Radios

 

[Matt308]

Cool! Looks they were radios using the current day High Frequency band. Interesting that they could regulate the radiated power for short range communications. I assume for tactical reasons. I'll pour over the stats when I get a little more time.

Thanks for the post!

 

[Salim]

Yeah, I'd definately like to take a look at this field. What kind of radio sets did they put on the fighter airplanes? What was their range?

I own a book about Japanese Naval Aviators in from 1937-45, and I what I saw was interesting on the wireless telegraphs and radio telephones used. It seemed that the radio telephones carried by single-seat fighters tended to be very short ranged... initially only 10 nautical miles, followed later on by an improvement that gave it a range of 50 nautical miles.

Just how did this size up to American, Russian, British, and German radio sets?

 

[MIflyer]

All US WWII Aircraft VHF Radio sets were crystal controlled, whether indirectly, such as the VHF ARC-5 or directly, such as the SCR-522. So there were no such things as channels in the modern sense, where the channels are controlled either digitally like modern radios or by a frequency synthesizer as in the older ones from the 50's and 60's. The frequency in use depended on the crystal that was used.

For the HF sets operating over the 1.5 MHZ to 18 MHZ range the SCR-274-N receivers and transmitters were controlled by setting the variable frequency oscillators to the desired frequency. Bombers, having radio operators to do the tuning task, had more options than did fighters when it came to HF. Fighters generally had to transmit on whatever the technicians had set up before takeoff.

Now, I assume that there were some standards for how close you set the different radios together, but I do not know what they were. Generally speaking, for AM voice communications you can go as close as center frequencies 5KHZ apart without too much interference.

Good question, though! I will ask some real experts I e-mail with.

 

[yahya]

VHF AM started to be used during WW II, when HF radios performed poorly had had to be replaced (An example is the British TR9 HF set from the Battle of Britain). Then, VHF became omnipresent on Allied fighters in Europe and the Far East with the SCR-522. Various frequencies between 100 and 150 MHz were used. Channel separation was at 100 kHz, then at 50 kHz. Note that during WW II the VHF emergency frequency of US forces was 140.58 MHz. Later, that frequency moved to 243 MHz, when UHF radios proliferation became omnipresent in the second half of the 1950s.