|[AMRadio] Ranger Modulation|
ltaft at charter.net
Thu Nov 16 12:06:03 EST 2006
Well, I tried...I wasn't right so now I'll be left
Sorry about the bad info.
73, Larry K2LT
Gary Schafer wrote:
> You can't reverse the plate leads on the modulator tubes because it uses
> negative feedback from a winding on the transformer. Reversing the plate
> leads puts the feed back in phase rather than out of phase. It will
> First check to see that you have proper grid current on the 6146. Low grid
> current will not allow full positive peak modulation because the tube runs
> out of steam with low drive. It is much more important to have proper grid
> current with AM than it is with cw. The tube has to have enough emission to
> handle the peak power 4x the carrier.
> Be sure the screen voltage is high enough on the 6146.
> Be sure that you are not overloaded - more power than the transmitter is
> rated for. If you have it loaded too heavy again the tube runs out of
> emission and will not allow the modulation peaks to go high enough.
> Try another 6146.
> Gary K4FMX
>> -----Original Message-----
>> From: amradio-bounces at mailman.qth.net [mailto:amradio-
>> bounces at mailman.qth.net] On Behalf Of Jack Schmidling
>> Sent: Thursday, November 16, 2006 10:28 AM
>> To: Discussion of AM Radio in the Amateur Service
>> Subject: Re: [AMRadio] Ranger Modulation
>> Larry Taft wrote:
>>> Try reversing the phase of the audio by swapping the output leads of the
>>> modulation xfmr.
>> First I swapped the tubes to no avail. I then swapped the wires and now
>> have a strange buzzing that I can not locate but it shows up on the
>> audio with the gain at zero. Don't know if I barfed something up or not
>> but I vaguely remember reading somewhere that this an an indication to
>> reverse the leads.
>>> Weak tube in the audio chain causing lack of gain needed for the
>>> positive peak.
>> Just ordered new audio tubes.
>> Now I notice another discrepancy..... the manual that came with it says
>> to adjust the mod current to 75-90 ma. The manual that Rick sent me for
>> the new version which I seem to have says 55-70 and no clue why the
>> Which is correct and should I make an allowance for using 6L6's instead
>> of 1614's?
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