[Milsurplus] BC-9 Loop Test: Scratching My Head.

[AKLDGUY .]

Split frequency would be possible where the BC-9 was working with a station
such as a command base where the receiver and transmitter frequencies could
be independently set.

But the BC-9 is a true transceiver. For a pair of them in contact, one would
need to be transmitting high and listening low, while the other would need
to be
tuned vice versa. How could that be accomplished in the present design?

I do not think split frequency is the answer to the problem. I'm still
unconvinced
that there isn't a wiring diagram mistake and the key should be shown
connected
to the capacitor and neither should connect to 120V B+.

73 de Neil ZL1ANM


On Sat, Feb 11, 2017 at 7:13 AM, Kenneth G. Gordon <kgordon2006 at frontier.com
> wrote:

> On 10 Feb 2017 at 4:13, Hubert Miller wrote:
>
> > The Q whether high or low isn't a dynamic figure while the tube
> characteristics are.
>
> True.
>
> > Q is just not responsible for what you are seeing.
>
> Well, I disagree, at least in part. It most certainly could cause at least
> SOME of what he is
> seeing since the "Q" directly effects the impedance, which is reflected
> into the tube's plate
> circuit. Differeing "Q"s will cause differing offsets.
>
> > We assume that all radios had to have netting ability.
>
> Now THAT is a question I had thought about too. In most military comms
> with which I am
> familiar, the receive frequency is very often NOT the same as the transmit
> frequency. In
> fact, sometimes it is far off. I am thinking of the common way the
> AN/GRC-109 was used for
> instance. In fact, I vaguely remember something suggesting this in that
> original document
> that Dave shared with us on how to use the BC-9 in service.
>
> Is it possible that this +/- 12 kc difference between the TX and RX
> frequencies was well
> known at the time, and was used effectively for their comms? "I'll
> transmit on such and such
> a frequency, and will listen on such and such a frequency". ?
>
> > Maybe that was not the case with this radio.
>
> Yes.
>
> > You could still use it to communicate. Like the example of the early
> Forest Service 33 MHz radios
> > that transmitted and received on differing frequency.
>
> And the common use of the AN/GRC-109, and many others too.
>
> > Miller effect appears at the grid. Don't ignore the larger change in
> capacitance and impedance
> > at the plate of the tube.
>
> See above.
>
> > As i suggested, you may want to try increasing the plate feedback ratio
> capacitor, C1-lower.
> > That will be a palliative, not a cure, though.
>
> On the other hand, I also suspect that there MAY be something we have
> missed in either
> the circuit itself or in the operation of the equipment. Perhaps there was
> a "field change" or
> modification which we don't know about.
>
> > Or, assuming you really want on-frequency operation, you could operate
> the set with the same
> > B+ on transmit and receive, say something like 90 volts max, maybe. Yes,
> your power out will
> > go down to 1/3 or 1/4, but you'll still be able to make demonstration
> QSOs.
>
> Yes. That is another good idea.
>
> But, folks like Dave and I believe the equipment should be operable in its
> original condition
> and shouldn't need any mods to make it work for amateur uses.
>
> Ken W7EKB
>
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