[Milsurplus] BC-611 MF vs low VHF

[Bob Wilder]

At the start of the war AM transmitters in the 30MC range drifted so badly 
that they were almost unusable.  I had a chance in 1948 to use a Japanese 
handheld that a ham brought back that operated in the 28-30 MC range and it 
used a single type 30 as a modulate oscillator and would drift 25-30 KC 
everytime it was keyed.  The US rigs in that range were not much better in 
the 1941-43 time frame.  Not only drift but most of those early 30MC AM 
rigs were bad about FM'ing also.


At 05:33 PM 3/30/2005 -0500, Bob Camp wrote:

>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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Bob & Carole Wilder
6032 Idlemoore Court
Theodore, AL 36582-4117
251-653-5274
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Asst USAF State MARS Director- Alabama
AF2HD/AFA2HD
{Ex W2ZRX, K4FEU, KG1BW, F7CP, W1HJL, W4NVH and W4RHW}

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