[ARC5] OT? bc-348 bfo question

[John Hutchins]

    DItto that -!
Hutch

On 9/13/2013 10:54 AM, Meir WF2U wrote:
> Fer,
>
> First of all the BC-348 was not designed to receive SSB. Receiving SSB is a
> bonus owing to the fact that there is a BFO in the receiver :-) ...
> The manuals don't define the amount of BFO injection. However, according to
> the manuals and by correct operating procedure of any receiver without a
> product detector but simple carrier insertion to the detector, CW is
> supposed to be received with manual gain control and not with AGC. The
> reason is that the BFO signal will reduce the gain if it's stronger than the
> signal coming into the detector as the AGC detector can't differentiate
> between the received signal and the BFO signal.
> The way to go around this in receivers with separate RF and AF gain control
> is to use manual gain control - no AGC, audio gain maximum and gain
> controlled with the RF gain. In case of the BC-348 the RF and AF gain
> controls are on the same shaft, therefore, as you discovered, the best
> reception is with MGC and the gain control is at the minimum position which
> gives the clearest audio.
>
> Nothing is wrong with your receiver; it's simply the way it was designed to
> be used on CW.
>
> 73, Meir WF2U
> Landrum, SC
>
>
> -----Original Message-----
> From: arc5-bounces at mailman.qth.net [mailto:arc5-bounces at mailman.qth.net] On
> Behalf Of Fernando - LU2DFM
> Sent: Friday, September 13, 2013 11:29 AM
> To: arc5 at mailman.qth.net
> Subject: [ARC5] OT? bc-348 bfo question
>
>
> Sorry if this is OT here.
>
> I'm repairing and aligning a BC-348 (E, M or P variant, don't know
> exactly which).
>
> The set is going on very well on AM so far, however the BFO injection
> level seems to be too low for SSB on strong signals. It's possible to
> get SSB on the headphones with MVC and _very_ low RF gain.
>
> All voltages and resistors values are ok around that stage with and
> without BFO on. The xtal filter is ok too (bandwith with xtal on is about
> 1-2 kc).
>
> The 2nd IF/CW osc. is the 6B8/VT93.
>
> Anyone knows what the level of the BFO is supposed to be?
>
> Thanks.
>