• 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.

backward swing on watt meter

airplane1

W9WDX Amateur Radio Club Member
Apr 15, 2005
1,051
32
58
Lebanon county PA
Hi, Question, I have a watt meter conected between the amp and antenna, now when it`s set for average watts it swings backwards, my meter on radio swings forward like it should. my swrs are 1.2 or less. all reports tell me that it sounds great and their meter on their radios shows upswing.

Can someone tell me if this is ok or a problem and if a problem can it be solved.

Thanks,
AP :?
 

The ONLY true peak reading watt meter readily available to read AM (amplitude modulation) is the Bird 43P.

There is also the Pal-Star WM-150, it is a true ACTIVE peak reading meter, if you do not have power to the meter, it will not read peak because it uses a IC-chip to control the meter display.
And less money than the 43P.



Link to Palstar ------------here

73
Jeff
 
So if I buy the palstar 150 it would be one of the better meters for my 11 meter cb setup, I just want to be close to knowing what my system is putting out.

Thanks,
AP
 
the kenwood sw200a has a true peak reading function that tested as very accurate in a meter shootout against other meters, some of the hansen meters have active peak reading too, hi res do an inexspensive peak board to convert your existing meter to true peak reading, http://www.hi-rescom.com/
 
Airplane: Two things to help make the answers to your question a little easier to understand:

1. You were probably over driving the amp, i.e. had the carrier set too high, which was why turning down the deadkey changed what the meter showed.

2. (This is Justin's point simplified, a bit :) ) You really shouldn't be using an AVG reading meter to see how much power your producing, because it's not very meaningful. You need to use a Peak reading meter, preferably an active peak reading meter (the most common one is the Bird 43P). If you can't find or afford an active peak reading meter, then at least use a passive Peak meter (Astatic, Dosy, Daiwa, etc), but realize that it won't be terribly accurate.

Hope that helps.
 
You can buy a used oscilloscope that will also indicate and do more than a $$$ peak reading watt meter. It can also be used for troubleshooting and aligning radio circuits as well. All one needs is a well designed interface circuit to input the RF enevelope, and those are simple to construct and readily available on the Internet. Downside is one must know how to operate a scope, whereas most meters are more straight forward to operate.
 
Now there's a gadget I should be selling. An inline envelope detector with a SO-239 on each end. Watch your demodulated audio envelope. Dead carrier will display as a straight line. And it won't matter what the 'scope's frequency response is. For that matter, a 5 MHz scope will probably look 'cleaner', since it won't be able to 'see' stray RF leaking from the detector into the 'scope's vertical input. Hmmmm.

Wonder why nobody offers that. Wait, I haven't checked MFJ. Sounds like the kind of thing he'd sell for half what I could afford to charge.

Gotta check that first, before I get too excited.

73
 
  • Like
Reactions: Slowmover
I was wondering if someone could describe this inline envelope detector? Something like a schematic or even a block diagram type description would be great.
 
airplane1 said:
Hi, Question, I have a watt meter conected between the amp and antenna, now when it`s set for average watts it swings backwards, my meter on radio swings forward like it should. my swrs are 1.2 or less. all reports tell me that it sounds great and their meter on their radios shows upswing.

Can someone tell me if this is ok or a problem and if a problem can it be solved.

Thanks,
AP :?

In a nutshell it's due to the meter (circuit) construction. If you have a passive AVG/PK reading meter it will be reading what we call quasi-peak. Sometimes this backwards swing can be caused by the components used, circuit design, sensitivity of the movement, or diode selection and or all the above combined.

For the radio yes turning down the dead-key will will allow more head-room. Stock finals are only good for a certain amount of power and once this limit is reached -- you can see a reverse reading.

If you pick up a Palstar unit this problem will be solved altogether because of the active circuitry within the unit.

The WM150 is a nice meter for CB or ham -- no nonsense and you can't beat the price.

;)
 

dxChat
Help Users
  • No one is chatting at the moment.
  • @ wavrider:
    sea que sea que,
    +1
  • @ ButtFuzz:
    C'mon let me take you on a Sea Cruise! (Maybe there is someone to talk to out there?)
  • @ ButtFuzz:
    Just for the Halibut.
  • @ ButtFuzz:
    Seems to be dead on the radio lately. I don't know if the conditions are horrible, or more likely my weak antennas. I may head up in the mountains on Wednesday and see if reception / transmission is improved.