Spectra observations continued. VCO/MLM/Codeplug ties.

[AR15Ron]

Ok, for all my searching and reading anything related to Spectra's I have never seen this mentioned on the site. Some people seemed to scoff at some of my previous notes when fooling with a 403 range UHF SP Spectra, but I have confirmed something, and maybe it is common knowledge but I have yet to read about it.

I recently bought a VHF A9 Spectra off Ebay. It was range 146-174. It had MLM 5.23 so of course I felt I had to swap in a 6.16 I had. Well after that I decided to clone my other VHF Spectra, range 136+. When I did that 159.0975 unlocked the VCO on receive! I thought that was funny, so I loaded the old codeplug back in and programmed in the frequency, now it locks. So I confirmed that the codeplug had something to do with VCO adjustments. So I went back, cloned the codeplug in, hacked all the numbers back to match, and then bitbanged the frequency range back to 146-174. Voila, VCO locks on fine. (wish I had known this before I physically modified the VCO in the low range radio!)

So, in conclusion, it seems absolutely possible to fix your VCO unlock problems simply by changing the frequency range by bitbanging. It is not unreasonable I think to assume that this could be exploited so that you would never have to do a physical VCO hack ever again.

I would think, if you have say a low split UHF radio and want a mid split, you might just luck out and get it working just that easily, without hacking up your VCO. I would also think that someone smarter than me could probably figure out how all that works and where it is located and you could adjust the VCO voltages simply by hexeditting your codeplug. I don't know if any filtering would be affected etc, it may be deaf as a post, but it should work.

If anyone has any information exploiting the MLM/Codeplug ties to VCO voltages/adjustments I would love to hear about it.

Again, I have yet to read anything about this, if this is nothing new perhaps someone should add this information to the model specific pages to save others from reinventing the wheel

Ron

[radio-link]

If anyone has any information exploiting the MLM/Codeplug ties to VCO voltages/adjustments I would love to hear about it.Ron

Just as an idea, maybe with some setting the LO oscillates below the RX frequency, with some others above? This drove me almost nuts with some german AEG radio, until I realized this :-)

[mancow]

So if I follow, you are saying you simply cloned a hi split codeplug into a low split spectra and it worked?

I guess I could dig out a low split uhf drawer and see what happens.


mancow

[AR15Ron]

So if I follow, you are saying you simply cloned a hi split codeplug into a low split spectra and it worked?

I guess I could dig out a low split uhf drawer and see what happens.


mancow

Well, it was a 146-174 split, I cloned in a low split VHF and all of a sudden my VCO unlocked on the local PD freq of 159.0975. I had the same problem with the radio I cloned it from and did a physical VCO mod about a year ago to make it work. Now, after I cloned the low split into the high split, I bit banged the model number back to the origional and then I bitbanged the band split back to the higher split, and the VCO locked back on. So yes, I suspect you could even go so far as to take a 403-433 split UHF and bang it into a 450-470 split and it would work. I'd love to try it! The thing I am unsure of is does this affect any of the filtering? Would the radio be 1/2 deaf in that frequency range or if everything would adjust together. Be interesting to try anyway, make those low split radios useful.

Ron

[VE3TUH]

By cloning your high split codeplug into a low split radio, you caused the low split vco aux lines to toggle at the high split specs. This caused your low split vco to unlock at frequencies that it previously worked fine on. The aux 1 and 2 lines to the vco toggle at different frequencies depending on the split of the vco. Your basic vco range is not determined by where the aux lines toggle, unfortunately. And simply by telling a low split vco that it is now a high split will not work, as seen by what happened with your vco unlock prob. Nice try, though.

Randy

[AR15Ron]

By cloning your high split codeplug into a low split radio, you caused the low split vco aux lines to toggle at the high split specs. This caused your low split vco to unlock at frequencies that it previously worked fine on. The aux 1 and 2 lines to the vco toggle at different frequencies depending on the split of the vco. Your basic vco range is not determined by where the aux lines toggle, unfortunately. And simply by telling a low split vco that it is now a high split will not work, as seen by what happened with your vco unlock prob. Nice try, though.

Randy

Have you tried it? Because it certainly seems like it works to me. If my high split radio became a low split radio from cloning and unlocked, why wouldnt the reverse be true. If you can make a radio lock out of it's bandsplit regardless of being in spec or 1/2 deaf or all out of calibration, I'd still be happy.

Ron

[VE3TUH]

Yep, I have. But not because I thought that I was going to change splits on a radio, rather because I accidently did the same as you, programmed a low split vhf with a high split codeplug. Ran into the same issues. Like I said above, that strip in the vco resonates best in a specific band, you cannot change that with programming. You can however do what you have done, which will change the aux toggle frequencies and cause the vco to behave differently, but the end result will never be satisfactory. Same goes for making a range 1 or 3 into a range 2 UHF, physical modification of the vco is neccessary, not optional.