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Part 15 AM transmitter - help needed

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dxer2_2000

Hi

I am running a small (400mW) AM stereo transmitter - the ASMAX-1 made in Greece.

I am using a 50m longwire unterminated (up off the ground - through trees). The signal is getting about 1km range max.


The problem I'm having is low freq buzzing in the audio - more so when in the stereo mode. How can I eliminate that? Even when I unplug the audio leads, the buzzing remains on an unmodulated carrier - so its more likely RF related?

TIA
dxer2_2000
 
We have the same Aspisys 100 mw transmitter in the eval lab and operates buzz-free. I assume you performed basic troubleshooting like disconnecting all the audio sources to make sure your buzz isn't part of your audio.

I've used the ASMAX-1 with a variety of audio sources from a lowly iPod to a professional audio processor (with the appropriate interface to adapt to unbalanced audio) and it's very clean. Our test unit has been in operation 24/7 feeding a ground mounted CB whip with no problem. It serves as a demo source for several Sony AM stereo receivers.
 
You may want to post on the "community radio" forum. It seems a lot more part 15 guys hang out there. However you will surely draw the ire of at least one poster we all know, love, and respect who no doubt will comment on your 50m antenna! ::) As for the hum, do as Bill says, make sure the hum is not coming from your audio chain, next would be to see if you have hum on your power lead. Not familiar with this unit but does it have a wall-wart or something?
 
Nostalgia said:
However you will surely draw the ire of at least one poster ... who no doubt will comment on your 50m antenna! ::)
Click to expand...

Unlikely, as said poster probably has checked the profile of the OP, and observed that the physical location of same is shown as Australia.
 
R. Fry said:
Nostalgia said:
However you will surely draw the ire of at least one poster ... who no doubt will comment on your 50m antenna! ::)
Click to expand...

Unlikely, as said poster probably has checked the profile of the OP, and observed that the physical location of same is shown as Australia.
Click to expand...

Helpful advice is a far cry from condenmnation, and to interpret such as "ire" is most unhelpful attitude.
 
The Buzz could be coming from a number of places.

Unplug your audio sources and see if that removes the buzz.

If that doesn't do it, it's likely your power supply, or a ground in the wrong spot.
 
I know when we got our eval unit there was no wall wart power supply with it so I had to fend for myself. You may want to check your power supply for any AC ripple on it. I don't know how good the internal filtering of the transmitter is as it may not be as forgiving of a poorly filtered power pack.
 
R. Fry said:
Nostalgia said:
However you will surely draw the ire of at least one poster ... who no doubt will comment on your 50m antenna! ::)
Click to expand...

Unlikely, as said poster probably has checked the profile of the OP, and observed that the physical location of same is shown as Australia.
Click to expand...
Mr Fry,
No I did not check his profile nor did I know he was from down under. Since he referred to "Part 15" which is good ol' USA FCC rules and regs I assumed he was from America. But admit it, had he been in the US you surely would have taken him to task!

The ::) may have injected a bit of humor to my post but what part of "know, love, and respect" could be interpreted as an "unhelpful attitute" Mr. Wells? Most in the broadcast engineering community know or know of Richard Fry, not only on this board but other technical forums like radio-tech and the SBE. I love to see him spar with the part 15 posters who just dont seem to get it, and trust me Mr. Fry, I do respect your knowledge and expertise in our field.
'nuff said.....
 
Nostalgia,

I simply meant too many people misinterpret Rich Fry's input as though he has some personal anti-part 15 agenda.
They are the ones with the unhelpful attitude.
Sorry if that seemed aimed at you.
 
The signal is so small it would never bother anything. At 1km, the signal is so weak that I had to use a Pioneer supertuner III-D w/ a 1.9m whip just to hear it. an ordinary radio would not hear it. That was the extreme range of the signal with a clear daytime channel. Any skywave would kill it. Also I live way in the bush, that no-one is likely to hear it anyway. There are only 2 local AMs here, so plenty of band to choose from during daylight.
 
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