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 swings lower power?

Yeah, I have seen it said many times on here they are not the best, but, whether on peak or RMS, it has the same response. It isn't just a 'swing' that follows audio, it is a drop. Maybe my terminology has been a bit of a confusion in this thread, too..

I just made a video, see if I can get it uploaded here...

EDIT:
OK. I don't know if Photobucket changed something or what, but for some reason I cannot get it to upload to there, and it is too big to directly upload, it is just over 2 minutes long.... It has been a couple years since using PB, but it says uploaded successfully yet "Someone has moved or deleted this image" appears when I go to do anything...

Edit 2:
Photobucket. They have a big button "Choose Photos and Videos" on the upload page. Yet in small words under it "To select multiple photos, hold SHIFT OR COMMAND as you click. Note: Videos are no longer supported Supported image file types include gif, jpg, jpeg, png, and bmp."

Anyone have a suggestion of a free video hosting site I can use to post a video here?
 
Last edited:
I kinda skimmed over all the response but from all I have read it seems the 939 either produces real forward power or it doesn't? It doesn't even matter if the 939 power is dirty if its forward average power is going up then the amp will respond in kind if the radios average power is going south then amps power will go south as well, Which is it? if you have a field strength meter in that Astatic meter use it Field strength meters are pretty good at showing the power that is going up with modulation or if it's going down from a DK. Determining the culprit should have been a 10-minute exercise not a Rocky IV training to beat the Russian event. LOL, Sorry, I'm in a bad mood and I'm taking out on this poor defenseless form.
 
Last edited:
  • Like
Reactions: Cutlass327
Hi OT03 - I had asked a similar question, "I'm curious as to what kind of mods were done to that radio" back a page or two. so if we have a broadbanded issue (more harmonics produced the amp is picking up and it's spread spectrum) - dropping power - or there is a "boxcar" issue and power does drop in both sideband and carrier because of a TX strip tuning or alignment issue. (Saturation flattop)

IT's far easier to swap out meters or borrow someone's bench and remove all doubt.
 
  • Like
Reactions: OldTech03
What does the DX44v dead key at lowest setting?
The difference between a 1 watt carrier and a 2 Watt carrier could be the reason you have "back swing", I say that because I have a few old school transistor amplifiers that like really low drive.
If you over drive the input, they will put out a large carrier (60 Watts) and fall back with audio.


But if the DX44v dead keys the same as the other radios and the amp works fine with it, the problem would be in the other radios, process of elimination.. :coffee:
 
Last edited:
Well, they're all just basically propely tuned and aligned now, no more ghosting or clipped modulation limiter.

I hadn't thought about the FS meter..

No offense taken, I know those days well!
 
I don't have the 44 hooked up at the moment. Gotta rework things to hook it back up again. Give me a couple days, my parts binding posts will be here Wed according to Amazon... trying to clean up a spaghetti factory explosion if wires here...
 
  • Like
Reactions: LeapFrog
1.75 to almost 5, then 70 to 130 on the "peak" setting. 70 to 40 on RMS using the DX939
The higher readings earlier were with the 5W DK which gives me 5 to 13W then 140 to 150W
 
Just remember #327, this is a process of elimination - once all the obvious stuff has been accounted for, then the simpler answers start to show up - and with more direction as to what may be happening.

I concur with LeapFrong on the "input" issue.

This may also point to the amp as having an internal issue we are not aware of.

One being, and this is only to provoke thoughts...

There may have been a part failure or a part swap in the input section of the amp.

For if you have DK and output - they seem low as far as AMP output, but there is more to it than just "low" - it swings backwards when you modulate.

Nomad gave a good suggestion earlier - lower the wattage either thru Deadkey, or AMC/ALC trimming - to remove the excessive power that if put into the amp - can cause it to clip - like really distort to square wave clip type stuff.

This may mean you have some type of swing mod in there and the amp distorts from the wide dynamic range the output of the radio has.

You said you have the radios tuned up - so I'm pushing that back to the back of the bench for the moment - for we may have a problem more with the amp - either thru assembly, poor parts selection (badly designed or not soldered well to begin with) or someone tweaked the amp for a different radio than what you've got.

This is why I asked about a monitor radio - if you have an amp that is VERY sensitive to the input power, it let's anyone within earshot of it's signal know that, because it pinches up audio or as some would call it start "FM-ing" and you see power drops because the meters aren't seeing RF at the frequency - its all over the spectrum - which you'd hear in the monitor radio just as bleedover if you tuned the amp of channel 1 and heard it all being done on channel 40 - that type of bleedover - with no antenna on the monitor radio to boot!

Radios and amps that start to bleed, lose power into the network as spread spectrum - which is more of a response to an overload input signal. Especially if - it's too strong and the amp can't do anything with it except clip and turn into a high-speed switch of DC and RF mixed together - and all you get is heat from it.

That same stuff as above, can happen to a regular radio without any help from an amp - it does the "backward swing" on it's own - usually due to a bad tune up or a poorly done drop in upgrade mod to a final or even an RFX75 install done wrong...the amp simply amplifies the entire effect...

Again, the radios' we are trusting are working right - so the process of elimination means it's now squarely on the amp and it's ability to take in power and produce...
 
  • Like
Reactions: Cutlass327
I'll try another antennaless radio later today.

Would it matter if the radio was connected on a selector switch? I have 3 radios on a 5-way switch (2 places not used), so the coax is only a fracton of an inch from each other inside that dial switch. Otherwise, I'll have to remove the coax from one.
 

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


      Top Bottom
      Back