Spectra 450-482 move to Ham

[jstigler]

I have a Spectra 45w dash mt 450-482MHz. I can pgm with RSS into the 440 range. Did the VCO mod to extend a bit. Seems if you ck AUX1 & AUX2 when watching AUX2 at 0volts in 445-465MHz range and it goes Hi to 8volts from 444-440. 445Mhz VCO volts is 2.9. It just seems this switch on AUX2 between 444 & 445 is a clue. Fail 001.

I have done all the caps and the radio is fine in it's normal range.
Thoughts!
Johnny

[jstigler]

Update 2:
Grounding the AUX 2 line allows the RX to work all the way to 440
However that is not the solution. It must go Hi for TX to work. TX is good down to at least 445
Something in the software needs to happen to fix this.
My opinion
Johnny

[N4KVE]

I too was faced with the same dilema in wanting to use a Spectra on the UHF ham freq's. Even if you get these problems addressed, the radio will still be partially deaf from 442-445 mhz. Those 450-482 radios just weren't made to work at 442 mhz. The front ends are real tight, & once you get below 445 rx, deafness occurs. My solution was to find a couple of the elusive 438-470 mhz Spectras which came as 15 watt motorcycle radios. They work great in the ham band, & rx as well as the Jap radios, but don't get the intermod. There is a fellow on the board here named Will who knows these radios inside & out who might be able to help you. Good luck. GARY N4KVE

[jstigler]

Thanks Gary for the input. I have an MCS2000 in the truck 403-470 and it is fine.
Never seen one of the Range 2 radios in Spectra.
This radio does have good Sens down to 440. 0.3uV or better.
Johnny

[Will]

There is a fellow on the board here named Will who knows these radios inside & out who might be able to help you. Good luck. GARY N4KVE

Thanks Gary, I sent Johnny an email.

You some times have to add 4 components and change a couple of other components to get them to receive really well. This is due to the receive being 440 to 446 mHz. Fortunately here is Socali, our receive is 446 to 449.99 mHz makes it easier.

[wa6jbd]

The filters can be moved down by soldering 1 to 1.5 pf 0603 chip caps across the each of the filter elements. If you really want to get elaborate like I have, you can order a supply of various values from .5 to about 3 pf, and individually tune each section. It takes a stead hand and some sort of sweep gear. I've been getting better than rated sensitivity, and response flat +- 1 db from 440-450.

[jstigler]

I checked the sens at 444-442 and it is useable. Below 442 I would need to tune as you describe.
I will get with Will on the real fix. I have the issue of aux2 flipping to Hi between 444 & 445 that kills RX below 445. That is the real issue I have. Short AUX2 to gnd and RX works below 445.
Johnny

[wa6jbd]

On the VCO, I've been lengthening the microstrip resonator with conductive ink to lower the frequency range. It takes care of both TX and RX frequencies. If you look, it's been cut shorter by a laser to tune it up in frequency to where it wants to be in the Range 3 radios. Just bridging the laser cut gaps is usually enough to get coverage across the 440-450 segment.

[jstigler]

I have the pin and have modified the length of the line. When I ground the AUX2 line to force RX below 445MHz the VCO is good. Sensitivity is acceptable down to 442. I just have to overcome the AUX2 line switching between 445 & 444. Perhaps it is software related. I did attempt the software mod to move the low freq from 450 to 440. No change.

[wa6jbd]

You shouldn't have to do anything with the AUX2 line. Here's exactly what I've been doing:

1. Modify software to allow programming from 440-450.
2. Program radio with 10 modes, in 1 MHz steps - 440.0 441.0 442.0 443.0 etc, up to 450.0 It may be helpful to go a bit beyond either end, your choice.
3. Once radio is programmed as above, step through channels. Stepping down from 450.0 , at some point the radio will FAIL 001.
4. Pull VCO, and lengthen the VCO microstrip resonator. Reinstall and repeat step 3. FAIL 001 should occur at lower frequency.
5. Repeat as necessary until it stays locked across the band.
6. Do not fiddle with AUX2 lines, do not bitbang the radio to think it's a range 2.

This is how I've been doing it, and I haven't run across a radio yet that couldn't be made to just work. I also retune the RX filter, and set the power and PA current to get constant TX PO across the band.

[Will]

You shouldn't have to do anything with the AUX2 line. Here's exactly what I've been doing:

1. Modify software to allow programming from 440-450.
2. Program radio with 10 modes, in 1 MHz steps - 440.0 441.0 442.0 443.0 etc, up to 450.0 It may be helpful to go a bit beyond either end, your choice.
3. Once radio is programmed as above, step through channels. Stepping down from 450.0 , at some point the radio will FAIL 001.
4. Pull VCO, and lengthen the VCO microstrip resonator. Reinstall and repeat step 3. FAIL 001 should occur at lower frequency.
5. Repeat as necessary until it stays locked across the band.
6. Do not fiddle with AUX2 lines, do not bitbang the radio to think it's a range 2.

This is how I've been doing it, and I haven't run across a radio yet that couldn't be made to just work. I also retune the RX filter, and set the power and PA current to get constant TX PO across the band.

That is a lot of work. Too many Spectras hacked this way have failed later on in life. They become unstable and noisy on both RX and TX.

[wa6jbd]

That is a lot of work. Too many Spectras hacked this way have failed later on in life. They become unstable and noisy on both RX and TX.

I'm unaware of a better way. I've done about a dozen radios this way, and so far, all have been rock solid, with no problems. I'm curious what the flaw in my methodology is. The only thing I've observed as even remotely a problem is that running wide open, the transmitter PO will fall from 40 watts to maybe about 32 from 450 going down to 440. I back it down to about 30 watts and it's constant across the band. As to instability and noise, none has been observed as yet.

[jstigler]

Thanks for the detailed info. I think my issue is the earlier ver of RSS that I attempted to move to 440. I will get the radio in question loaded with a known good 440 RSS and bet it works as planned.

Thanks for all the help.
Johnny

[Will]

Johnny,

I do not think the RSS is your problem. Check your EMAIL.

[jstigler]

RSS ver06.00.05 did the trick to get this radio below 445MHz. It no longer has the AUX 2 issue below 445MHz. I need to clean up the VCO a bit to get the TX locking at 455MHz and tweek the front end of the RX if I need to listen below 442MHz.

The goal is to use this 450 & a 420 Spectra with a Pico Dop unit to make a universal dopler for tracking undesired signals in mostly the Ham Bands. Could be a little faster than the IFR and a Beam.
Johnny S.