Sidebar Sidebar
  • You can now help support WorldwideDX when you shop on Amazon at no additional cost to you! Simply follow this Shop on Amazon link first and a portion of any purchase is sent to WorldwideDX to help with site costs.

Amp reduces gain when going from standby to operate

H

Highland Ranger

Active Member
Aug 28, 2005
141
9
28
New amp, ameritron AL-80B.

When switching from STBY (standby) to XMT (operate) the amp has the effect of reducing the receive gain.

Does not happen when the amp is off - only when energized.

Is this normal?

(AMp has the grid current protection and QSK board in it)
 

No, it isn't normal. It means that there is some attenuation in the 'by-pass' circuit in the amplifier. If it uses a mechanical relay, the contacts of that relay should be checked, maybe burnished. That's not the only possible source of that attenuation but it's one of the most likely.
Also, depending on the design of that amplifier, just changing the switch from 'Standby' to 'Operate' really shouldn't make any difference except to power that change-over relay. I don't understand why it would make any difference. That circuit would be a good place to check too.
Have fun.
- 'Doc
 
  • Like
Reactions: 1 person
Hmmmm - I thought it had no relays - using that board that does the electronic switching but I heard something clacking in there so must use a relay for this circuit.

Coax is all tight - transmitter to amp, to LP100a watt meter, to tuner to low pass filter and out to antenna. SWR is good.

Brand new, factory fresh - I guess a call to Ameritron tomorrow.
 
  • Like
Reactions: 1 person
Remove the keyup lead.
If it stops, your keying lead is grounding the internal relay circuit causing it to pull up.
All the standby switch does is prevent the internal relay from operating.
If you lose your receive without the keyup connected, there is an internal issue.
Good luck.
 
Look hard at the connections for the QSK board. Normally when you're transmitting, you're not immediately concerned with receiving. I'm not familiar with the AL-80/QSK configuration - can you disconnect the QSK circuitry (switched or hardwired??) and see if there's some interaction?
 
Thanks for all the replies.

Still waiting to hear back from Ameritron. Their tech support line comes back as "this is a non-working number" so I have a ticket open thru the web site.

When I flip the switch from STBY to OPR, the XMT light lights up and I hear a relay clack inside.

When I key up I don't hear a relay.

Output is fine, tunes fine - only issue is a drop of about 3s units when I go from standby to operate.

QSK board is internal, so before I go messing in there on a brand new unit going to see what they have to say. Agree though, seems like that may be the culprit.
 
Reply from Ameritron:
-------------------------------------------------------------------
Lamps on the QSK board appear to be blown and is mostly caused by SWR spikes back from the attenna. They generally act similiar to fuse in this application. If you ohm them out, they are probably open. Part number:355-4012 .62cents each. Can be ordered at ameritron.com, or over phone. They may have Blue, yellow, or black leads, all are interchangeable.
----------------------------------------------

I guess like my friend says, don't buy an MJF product unless you appreciate a learning experience.

I hope this is the issue.

By the way - amp was protected by an LP-100A watt meter set to trip out at 1.5 SWR.

Rig was pre-tuned using an MFJ-989D to 1.0 SWR.

So I don't see how SWR spiked . . . . .

Still need to go in there and check them.
 
Highland Ranger said:
Reply from Ameritron:
-------------------------------------------------------------------
Lamps on the QSK board appear to be blown and is mostly caused by SWR spikes back from the attenna. They generally act similiar to fuse in this application. If you ohm them out, they are probably open. Part number:355-4012 .62cents each. Can be ordered at ameritron.com, or over phone. They may have Blue, yellow, or black leads, all are interchangeable.
----------------------------------------------

I guess like my friend says, don't buy an MJF product unless you appreciate a learning experience.

I hope this is the issue.

By the way - amp was protected by an LP-100A watt meter set to trip out at 1.5 SWR.

Rig was pre-tuned using an MFJ-989D to 1.0 SWR.

So I don't see how SWR spiked . . . . .

Still need to go in there and check them.
Click to expand...

just send the thing back and tell them you want your money back because there was NO customer caused spike
 
When you go from Standby to Operate, the relay should not be engaging. I do agree that the QSK board is likely at fault here. That's the first thing I'd be looking at, and it seems you're already on that path. That's an amp I wouldn't mind having. Good luck on it!



~Cheers~
 
  • Like
Reactions: 1 person

dxChat
Help Users
  • No one is chatting at the moment.


      Top Bottom
      Back