[Milsurplus] BC-611 MF vs low VHF

[Bob Camp]

Hi

 From the standpoint of the antenna and overall performance the higher 
frequency would have been much better.

In order to easily run at 30 MHz you would have to be able to plug in 
third overtone crystals in the crystal oscillator. As far as I know 
that just wasn't an option in 1940. Simple production of fundamental 
crystals was a significant bottle neck through 1943.

If you went with fundamental crystals you would be stuck with a 3X to 
6X multiplier. Depending on weather you do it in one stage or two you 
add some power or lots of power to the total current drain. Two stages 
probably are more likely in order to keep the sub harmonics down.

The technology of crystals changed dramatically by the end of the war. 
Of course that didn't help the stuff we fielded during the war.

The second thing that probably gets you on a 1940 design is the 
development of high frequency powdered iron compounds. Again it's one 
of those things that changed a lot during the war. You could make a lot 
better small 30 MHz tuned coil in 1946 than you could in 1939. It's 
probably not as big an issue as the crystals, but I suspect it did have 
an impact.

	Take Care!
	
		Bob Camp
		KB8TQ





On Mar 29, 2005, at 11:25 PM, Hue Miller wrote:

> This silly question popped into my head: as the BC-611 was
> crystal controlled, would it not have been advantageous to
> build it to operate on 10-11 meters rather than as low as 3 MHz?
> The antenna would have been effectively 10x as long ( at
> frequencies most advantageous to this comparison ) and with
> a lot more radiated power. I am leaving out the issue of how
> to communicate to armored vehicles. -Hue Miller
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