[Johnson] Johnson 500 Spot Level

[hamfish at comcast.net]

Dave,

Sounds like all is normal with the 500. The last few years I've only been on
75 meters AM phone. In the last week or so a 40 meter antenna has been
strung up between some lodge pole pines. I can hear the spot signal on both
bands. But I will mention the noise level on my R390/A's are about zero.
There is something to be said about living in the sticks. Low level of
income in La Pine, OR and fewer China noise makers. 

I can't think of anything that wasn't or isn't vintage with my 500. It is
paired with a 56 contract Motorola R390/A and a dowkey T/R relay. The spot
signal isn't jumping out of the speaker, but easy enough to hear with the
volume (local gain) control set between 1 & 2 and BFO turned on. 

Could RFI be the real issue?

Regards,
Craig

-----Original Message-----
From: David Harmon <k6xyz at sbcglobal.net> 
Sent: Friday, August 2, 2019 12:17 PM
To: hamfish at comcast.net; johnson at mailman.qth.net
Subject: RE: [Johnson] Johnson 500 Spot Level

Hi Craig....thanks for answering.

Both these tx operate just like you mentioned with the VFO  vs xtals.
At 10ma drive....I can't hear the zero signal over the normal band noise on
the lower bands...it is very low on the quieter upper bands too....but
audible.
Both tx have been totally gone through recently....aligned
etc....everything.
Both receivers are Collins A-4 and are in outstanding condition etc....all
the usual caps replaced, tubes, alignment etc etc.
Both can hear signals below 1uv so I don't think either tx or rx are having
a problem....just that the 500 does not have a high enough spot level to get
out of its cabinet.
Tell me about your setup that has a useable spot level and what receiver do
you use?


73

David Harmon
K6XYZ
Sperry, OK


-----Original Message-----
From: hamfish at comcast.net [mailto:hamfish at comcast.net]
Sent: Friday, August 2, 2019 2:00 PM
To: 'David Harmon' <k6xyz at sbcglobal.net>; johnson at mailman.qth.net
Subject: RE: [Johnson] Johnson 500 Spot Level

Hello Dave,

Looking at page 46 in the owner's manual downloaded from BAMA, do you arrive
at the typical dial readings? Particular the drive and PA Grid values are
important. The item noticed with my Junkston "500", is the difference
between the drive setting using a crystal vs VFO. But once the PA Grid is at
10 mils, the spot signal heard is the same.

Could the sensitivity of the receiver be lacking? Without reviewing the
schematic, could the 5763 be getting weak? 

Regards,
Craig

-----Original Message-----
From: johnson-bounces at mailman.qth.net <johnson-bounces at mailman.qth.net> On
Behalf Of David Harmon
Sent: Friday, August 2, 2019 11:29 AM
To: johnson at mailman.qth.net
Subject: [Johnson] Johnson 500 Spot Level
Importance: High

Both my J500 have very low spot levels which make it difficult to zero the
VFO to the receiver.
I have a few ideas for a mod to increase this level but I thought I should
check to see if anyone else has had this problem and what was done to
increase the spot level.
Both transmitters are working to spec with no problems.
Anyone have any info?

Thanks...

73

David Harmon
K6XYZ
Sperry, OK


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