Warning: Creating default object from empty value in /homepages/11/d132647312/htdocs/Amfone/mkportal/include/SMF/smf_out.php on line 47
Johnson 500 Zero Level **FIXED**




 
The AM Forum
September 15, 2019, 12:52:25 PM *
Welcome, Guest. Please login or register.

Login with username, password and session length
 
   Home   Help Calendar Links Staff List Gallery Login Register  
Pages: [1]   Go Down
  Print  
Author Topic: Johnson 500 Zero Level **FIXED**  (Read 418 times)
0 Members and 1 Guest are viewing this topic.
Dave K6XYZ
Member

Offline Offline

Posts: 93



« on: August 02, 2019, 03:31:18 PM »

I have two J500 transmitters operating normally with no problems.
Both have been recently serviced and aligned by myself.
The spot level is so low on all bands that I am going to have to develop a mod to fix this.
But....I thought I should ask the group if there is an already existing mod that is being used that I don't know about.
I am using two 75A-4 receivers as well....both are operating normally and have the usual caps replaced and both are aligned properly.

Looking forward to anything anyone might have on this problem.
Logged
W9BHI
Member

Offline Offline

Posts: 361


« Reply #1 on: August 02, 2019, 08:23:36 PM »

There is a mod to increase the level of the spot signal that is in the Johnson Ranger manual.
The VFO and osc circuits are the same.

Don W9BHI
Logged
Dave K6XYZ
Member

Offline Offline

Posts: 93



« Reply #2 on: August 02, 2019, 09:03:09 PM »

There is a mod to increase the level of the spot signal that is in the Johnson Ranger manual.
The VFO and osc circuits are the same.

Don W9BHI

Thanks Don....I'll take a look.
Logged
Dave K6XYZ
Member

Offline Offline

Posts: 93



« Reply #3 on: August 03, 2019, 02:35:26 AM »

There is a mod to increase the level of the spot signal that is in the Johnson Ranger manual.
The VFO and osc circuits are the same.

Don W9BHI

Don....I had forgotten about the ability of the Ranger to increase the spot level by adding a strap on the function switch.
The 500 is sort of similar but I don't see a way to increase the level without some re-wiring.
If you have a way of increasing the spot level....please post your mod as there are a number of guys that have asked me about it on private email.

Thanks...
Logged
Dave K6XYZ
Member

Offline Offline

Posts: 93



« Reply #4 on: August 05, 2019, 06:06:40 PM »

The only clean way I could see how to increase the spot/zero level without any clip lead haywire was to connect a length of Mini-8 to the J500 SSB connector then to the A-4 antenna lug.
I used a PL-259 connector on the tx end and a single lug at the rx....no shield to gnd on the rx....this caused a lot of buzz and hum in the receiver...don't do this.....read on.

After looking at the schematic of the SSB input I removed the 2x100~ and .01uf from the wafer sw and TS leaving the coax from the SSB connector connected to the 2 lug TS.
Now....there is only the internal coax shield connected to the TS mounting lug and the center conductor connected to the other now vacant lug on that TS.

I experimented a bit more and came up with a different way to pick up the spot signal that works well without causing any problems.
There is no DC connection through the Mini-8 to the rx.....just an insulated stub added to the SSB coax conductor lug on that TS inside the tx.
The stub is long enough to be positioned very close to the 5763 driver.

At the rx antenna lugs a stiff insulated copper wire is close wound around the coax for a couple of inches with the wire’s open end connected to the rx ant terminal screw.
I removed the outer covering and braid of the Mini-8 so the wrapped wire is as close as possible around the still insulated center conductor.
It works well....I would like to have a higher spot level on 80mtrs but its ok......the rest of the bands are great.

The Valiant is very similar and I expect if more spot level is needed this same mod could be tried.
Logged
Pages: [1]   Go Up
  Print  
 
Jump to:  

AMfone - Dedicated to Amplitude Modulation on the Amateur Radio Bands
 AMfone © 2001-2015
Powered by SMF 1.1.21 | SMF © 2015, Simple Machines
Page created in 0.065 seconds with 19 queries.