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MikesRadioRepair Reviews Asymod iii HiFi Board

unit_399 said:
Wonder what it costs ???

- 399
Click to expand...
At least one hundred dollars for just the populated pcb, maybe several hundreds for a radio that's been pre-setup?
eBay, has them I think.
Robb said:
Think it is limited (by what I've read/heard/watched) to the freq response of the mic and whatever outboard gear is being plugged into it. Didn't see him adjust anything except the freq feed from the sweep gen into the radio. In fact, he even pushed the envelope and put 10hz-35khz audio, and the radio still transmitted it. It needs some limiting or adjustment capacity - IMO . . .
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Another reason why these board do not provide great audio, only the platform that needs to be configured and ran properly to get "great audio" & still keep a clean station.
 
So long as the operator uses some audio gear and processing, and knows how to use them, it should have outstanding audio. Not the issue - IMO.

I think it is a bit (?) irresponsible to run that much bandwidth on the CB band. Like I said earlier, even 5k or 6k wide can be plenty if you manipulate it right with the right gear and mic. The very reason I wrote the series of articles on HiFi CB - in the first place. 5khz wide is the line in which it encroaches on the adjacent channels. IOW - bleedover.
 
The biggest offenders of bleeding multiple channels don't have any interest in wideband audio or one of these boards.

I have a few locals with "normal radios" equipped with factory 3khz filters that splatter 5 to 10 channels. One takes out half of the band tuning up his phantom with a 1k tone.
 
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543_Dallas said:
The biggest offenders of bleeding multiple channels don't have any interest in wideband audio or one of these boards.

I have a few locals with "normal radios" equipped with factory 3khz filters that splatter 5 to 10 channels. One takes out half of the band tuning up his phantom with a 1k tone.
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Right.
But the other 'blleedover' you are talking about is caused by harmonics.
In the case of the asymod board, it is fundamental freqs.
Big difference
 
Robb said:
Right.
But the other 'blleedover' you are talking about is caused by harmonics.
In the case of the asymod board, it is fundamental freqs.
Big difference
Click to expand...

Bleed over is a nuisance no matter how you choose to cause it. Some offenders are worse than others.
 
Why limit it to 5k? In DX does it matter? And short of being a prick, is anyone local using an adjacent channel to the local channel?
The NRSC standard of rolling off sharply at 10k is just fine.

Of coarse I love it when I hear a good sounding 20-20k station like 225 jammimg in GA.
 
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undertaker said:
check out the web site radios are about 600.00 for a 955hp...JOKE!!!
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Let's just say the man knows how mark-up works, if someone had a bill of materials and the pcb layout, this could be recreated for much much less than the asking price.

Too bad MMM didn't patent his device, I.m.o. he could have. (Just leave CB out of the description...)
 
LeapFrog said:
Let's just say the man knows how mark-up works, if someone had a bill of materials and the pcb layout, this could be recreated for much much less than the asking price.

Too bad MMM didn't patent his device, I.m.o. he could have. (Just leave CB out of the description...)
Click to expand...

MMM didn't design the board. You can find the guy that did on the amfone forum.

http://amfone.net/Amforum/index.php?topic=23833.0

There has been a lot of discussion elsewhere about if he could have patented it. Lost of similar circuits that have been around for decades.
 
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543_Dallas said:
I remember a YouTube video from the early days where he injected a 20k tone to show the capability of the board. On a receiving radio he showed what looked like a carrier 2 channels up and down. Not sure what the newer generations of the mmm board are capable of.



Exactly. Turn down the highs on the eq. Most rack gear will not even pass frequencies as high as mike used to prove his opinion.
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They boards are capable of 20k but from what I understood is MMM added caps to limit the response to 10k.
 
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unit_399 said:
Well ... maybe if someone makes a receiver that will handle 20-22khz.

- 399
Click to expand...
For anyone looking for a cheap Hi-Fi wideband multimode receiver,
I'm leaning towards getting an RTL-SDR and an LNA4HF (filter/amplifier) for under 70$ total shipped, but requires a computer/laptop to operate.

That gets you an easy 30 KHz receiver, with a pass filter to block out the high powered commercial FM Broadcast stations that commonly interfere and overload the cheaper software defined radio receivers front end. You can just a receiver anyway you like, squelch, AGC, width, filters, NB +more.

Though you could use almost any low noise amplifier and bandpass filter with an RTL-SDR (cheap); I just think the LNA4HF looks promising. Without a filter the local fm stations cause overload issues, but the receiver has an extremely wide range tuning range 150 KHz to over 3 GHz (I think), with many modes, AM, FM, SSB, CW, and more.

The SDR# software is free, and many great plugins exist.

Just don't transmit right next to it, without first disconnecting the antenna or switching it out of circuit with a relay or something! (I do this to be safe, I don't know if the SDR will die from an up close or extremely strong signal)

I dummy load test CB's right next to the computer and watch the results in an "RF spectrum", it's too bad you can't sample a huge range like a spectrum analyzer can. But it's good for sampling transmitted audio, and looking for harmonics. (Leave the SDR antenna plugged in, and use a dummy load near the computer/SDR antenna.

Cheap Hi-Fi receiver, and an improvised "ghetto tech" style testing tool in one package!


I think Mike did a great job on the review even though he did not exceed 100% modulation, I wish he tested everything, including the asymmetry lol. (y)
 
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