From: Garey Barrell 
Subject: Re: [drakelist] T-4x, R-4 Transceive RX Question


George KB2Z wrote:

> Hi Garey,
> 
> When zeroed with rear control, the meter stiil reads as far past 60db as 
> it will go. In standby or with rf gain full CCW.
> I dont see anything in the manual that specifically addresses the meter 
> adjustment. Would adjusting the bias with the R40 meter sensitivity pot 
> bring it down or should I look for something else?
> 
> Again thanks, George KB2Z
> 
> 
> 
> At 09:44 AM 1/30/04 -0500, you wrote:
> 
> 
>> George KB2Z wrote:
>>
>>> Good morning list,
>>> Things are moving right along with the T-4x quirks.
>>> I have a question about using in x-ceive mode.
>>> Things seem to be working as expected.
>>> When transmitting the S-meter on the R4 moves all the way to the 
>>> right side. It dont slam but does do +60 over.
>>> Is this normal for the T-4x, R4 pair?
>>> Thanks in advance, George KB2Z
>>
>>
>> George -
>>
>> It should do exactly what it does when you put the receiver in Standby 
>> mode with the transmitter disconnected.  If it goes WAY over, you 
>> probably need to look at the S-Meter adjustment.  When the RF Gain is 
>> turned full CCW, the S Meter should read 60 over, (Full scale,) no 
>> more, no less.
>>
>> 73, Garey - K4OAH
>> Atlanta

George -

OK.  Well it's been a while since I worked on my R-4.   The RF Gain CCW method 
is what was used for the R-4A/B receivers.  The earliest R-4A receivers (almost 
identical circuitry to the R-4) changed over to setting the S-Meter to 60 over 9 
with the S-Meter Cal pot while the RF Gain is full CCW.

Anyway, the very last paragraph in the R-4 Manual is labeled "Bias and S-Meter 
Adjustment".   For the R-4 they used the calibrator as a
"standard" signal and 
adjusts the internal S-Meter Cal pot for 20 over 9.  If your manual doesn't have 
this paragraph, let me know and I'll transcribe this one.

The Rcvr SENS adjustment, (R87, just to the front of center in the receiver,) 
set to -1.35V is very critical and determines the overall AGC performance of the 
receiver.

I suspect if you make the S-Meter Cal adjustment (R40, under chassis on a 
component board right behind V5, just to the rear of center in the receiver,) 
using either the calibrator method OR the RF Gain full CCW it will be very close 
to the same.

Let me know if I can help further.

73, Garey - K4OAH

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