Batboard

I have a 6 channel Low Band Maxtrac on 29.7 - 36MHz. Power output is 60W. The radio was manufactured in October 1999. I have researched all the excellent information on Batlabs and the Repeater Builder site but have a few questions:

- I understand that the last version of the RSS is R07.02.00a dated Jun 1997. As my Maxtrac was made in 1999 , I guess I will probably need version R07.02.00a to avoid the "codeplug too new" problem. BUT does anybody know if RSS version R06.01.00 dated Dec 1995, which I already have, might work OK?

- Will Maxtrac Lab RSS version R05.30.00 be able to program my Maxtrac?

- If Maxtrac Lab RSS will work , is there any reason NOT to use it?

- I understand that version R07.02.00a supports the Shift Key trick for out of band programming. I only need to program the Maxtrac down to 29.400MHz (ie. 300KHz out of band). Will there be any TX power or dev or RX sensitivity issues when progged down to 29.400MHz. I've read about the 6m mods but there is not much commentary on 10m alignment.

- Is there a programmable Low power level (such as 25w) - or is it only 60w UNLESS you start adjusting power in RSS service mode? I read that for 6m Maxtracs , you cannot lower TX power in Service Mode RSS below , say 30W , without upsetting things.

- I understand that there is a heavy duty version of the power lead. I don't have the original power lead for the 60W Maxtrac but have plenty of official leads BUT all my other Motorolas only run a max 25W. Will a "25W" power lead be OK for a 60W radio or will the cable melt!!

- Is the squelch pot in the same location as the 6m Maxtracs - and does a Maxtrac manufactured in 1999 still use manual SQ adjustment or can you do it using RSS?

Many thanks

Okay, lets see...

As to question 1: Any version of the Maxtrac RSS will work fine so whatever version you have or want to use should be fine. "Codeplug to new" doesn't apply to the Maxtrac.

Question 2: Yes, lab will work.

Question 3: No reason not to use it unless you are re-initializing a blank logic board. Lab might actually be a little advantageous as it should let you go out of the band split without having to use the shift method.

Question 4: Since you are only going 300 khz out of band I don't imagine there will be too much of a difference with TX power and RX sensitivity. If there was a difference it would probably be minimal.

Question 5: TX power is adjusted through the service menu and I'm not sure of any possible adverse effects of going too low.

Question 6: Beats me.

Question 7: I would assume that the squelch pot is in the same place although if it isn't it'll probably have "SQL" stamped on the board right next to it. I'm pretty sure that regardless of the manufacture date the squelch adjustment would still be an internal pot.

Hope this helps.

Many thanks indeed Joe for the very helpful reply.

Any idea if RSS version R06.01.00 supports the Shift Key trick? I understand with the Maxtrac that the Shift Key trick did not work with early versions of the RSS (ver R05...) and you had to HEX edit the RSS.

If you use an earlier version of RSS which does NOT support the Shift Key trick, does this then prevent the future use of the Shift Key trick with version R07.02.00a. With other Motorola RSS, the Shift Key trick was REMOVED (not added) in later versions which you had to avoid!!! Is it a "reverse logic" with the Maxtrac?

Out of interest, any idea how low you can program a 29MHz Maxtrac before any realignment is necessary/VCO goes out of lock?

Are there any front end cores to align assuming you go a few MHz out of band - the 6m Maxtrac front end cans are "empty" (I think) and you need to add brass screws.

I think I will eventually implement the 32 channel/scanning mod but will get the Maxtrac sorted with the basic 6 channels initially.

Thanks again

I have never found an issue with "codeplug too new" with the trusty old Maxtrac.
I have run into a couple versions of LAB that would not let you use the "shift" method.
If you have a version of regular Maxtrac RSS that lets you program what you want, stick with it.
As for "how low can you go", I played with one that went down to 26 mhz.
If you are just going to use it in the usual FM part of 10 meters, I seriously doubt you would need to re-tune ANYTHING.
Small chance that the VCO steering line voltage would need adjusting, but I would think not.
Unless you know someone has played with it to make it go just above its design split (say make it work at 37 mhz) it won't need anything.
The heavier power cable is a little bit of overkill. Better if you have one, but the standard one will work.
Book says 17 amps at 60 watts, but usually it is more like 15 amps from what I have measured.
If you use the RSS and set the TX down to 30 ish, the current draw is around 10 amps.
As long as you are not running long runs of small guage wire you should be fine.
I have not seen any of the low band (10 or 6 meter) transmitters act spurious when setting the TX low, even going VERY low.
I have seen the VHF, UHF, 800 and 900 High power PA's sometimes get weird when set below about a third the rated power.
Not all of them do it, but my rule is to avoid going below about 50 percent power on any PA just in case.
All of them become inefficient if you turn them down too low, and the just make heat, and get weird.
Assuming you have the 16 pin board, you can blank and re-initialize the radio and make it a "High signalling" version with 32 ch, priority scan, "alias" the channel numbers, etc.
They make a fairly good 10M radio.

"If you use an earlier version of RSS which does NOT support the Shift Key trick, does this then prevent the future use of the Shift Key trick with version R07.02.00a. With other Motorola RSS, the Shift Key trick was REMOVED (not added) in later versions which you had to avoid!!! Is it a "reverse logic" with the Maxtrac?"

The Shift-Num method of data entry is a feature available in some releases of software. Using it doesn't affect the radio, the radio doesn't control whether you can do it or not. It's just the user interface. Once you enter an out-of-range frequency and get it into the radio, the radio will do its best to operate there. If you then read the code plug with another version of software, it may complain if you try to change the freqs, and if the Shift-Num method isn't available, your only recourse is to hex-edit the MDF file. It's just there for user convenience.

"Out of interest, any idea how low you can program a 29MHz Maxtrac before any realignment is necessary/VCO goes out of lock?"

Probably 1-2 MHz. That's typically what a 42-50 MHz radio will do.

"Are there any front end cores to align assuming you go a few MHz out of band - the 6m Maxtrac front end cans are "empty" (I think) and you need to add brass screws."

You'll have to add ferrite material (cores or steel screws) to some/all of the front-end coils to bring them lower in frequency, but don't expect a world of difference. The whole front end is wide-band and you might only gain a couple of dB in sensitivity at the band edges. They use different coil/capacitor combinations for each of the various low-band splits.

Comments on some of the other questions that were asked earlier:
The 60w radios draw around 12 amps. While you won't have a power cable melt-down, you may incur a significant voltage drop by using a cable meant for a 10-25w radio. The 25-60w power cable is only one or two wire gauges bigger but also has a larger fuse (probably 20-25 amps). If your going to install this into a vehicle and have power leads longer than 6 feet, I'd recommend the high-power cable.

I'd strongly recommend you only use the lab software for blanking a radio. Stick with regular software for initialization and all other programming as it'll have more models to choose from and do some cross-checks with option selection that have been purposely defeated in lab.

If you find answers to all of your questions, consider writing something about your experience and the results and submitting it to repeater-builder for publication. As you noted, there's nothing there for the 10m radios yet. Contact me via PM for more details.

Bob M.

Thanks everybody for all the useful feedback.

As recommended, I will stick with the regular (non-LAB) RSS for basic programming.

Anybody know if version R06.01.00 allows the Shift Key trick? I've previously HEX edited some GP300 RSS and it is much easier to do than it looks!!!...but its even easier to just use the Shift Key trick.

By the way , I found that the GP300 Shift Key trick works for +/- 5 MHz out of band - any further out of band programming required me to HEX edit the MDF file... the UHF GP300 worked perfect at 8MHz out of band with practically NO loss of RX sensitivity... although my GM300 mobile was a bit deafer.

I was very surprized that my Maxtrac was made in Oct 1999 (from serial no) and "ordered" (printed on box) in May 2000 - I was expecting it to be 10 years older!!! Much of my more "advanced" Moto stuff is actually 3/5 years older!!! I guess that the Low Band radios continued to be manufactured after the VHF/UHF/800MHz radio were replaced with later models.

I also noticed that the CDM1550/GM360 low band "replacement" for the Maxtrac also has identical "narrow" band splits on Low Band ie. 29.7-36MHz etc. You would think that today it would be possible to have a wide band Low Band radio which covered 29 to 70MHz !!!

For the benefit of others, I just want to comfirm what I had read on Batlabs/Repeater Builder - that the model number does NOT indicate which split the radio is on!!!

When I searched on my model number D51MJA....A3AK , all the matches were 42-50MHz radios. There was also several comments about "type 3" splits etc. I became convinced that an ..A3AK was probably a "3rd split" ie. 42-50MHz.

In the end, my expected 6m Maxtrac turned out to be a 10m Maxtrac - which is 100% OK and I was never misled by the seller but I guess it could have been a 36-42MHz version!!

I have now successfully programmed my 10m Maxtrac with 6 channels using RSS R07.02.00a - the Shift Key trick worked great!!

I've only used the Maxtrac in RX mode as I need to get some higher value fuses for the power lead ( I guess 7.5A/10A fuses will blow running 60W ?)

In band sensitivity is great. Sensitivity 2MHz out of band is OK - maybe 5dBm down but still very useable. I've not yet checked sensitivity just out of band (29.6MHz) but I think it will be 100% OK.

I am now about to try and mod the Maxtrac to 32 channels with scanning etc. I have researched all the excellent articles on Batlabs/Repeater Builder but have a few more questions:

- Do I actually need to "manually" read the Xtal Ref, tuning data number and measure the voltage on P1 ie. open up the Maxtrac and look for the labels - OR can I just extract the data from the regular RSS Service Menu?

- When using Lab RSS to Blank , can I use option "Blank Board with Extended Codeplug , SAVE TUNING DATA (rather than Clear Tuning Data)? I will not be using a "replacement" logic board - just the original board. I will definately note down the Service Menu tuning data before I start (just in case), but does the SAVE TUNING DATA option avoid the need to start inputting values?

- Are the tuning values extracted from the Board Replacement section the same values as shown in the Alignment section?? (apart from Ref Xtal data)

Thanks

The crystal data is two - four digit numbers on a tag on the crystal.
The seven digit tuning data is on a hand written tag usually in the same area as the crystal, or somewhere on the RF board or shields.
Meaning under the removable shield on the RF board.
There is no other way to get that tuning data or crystal data.
The two above sets of numbers must be found inside the radio.
The other tuning data is values of the alignment for deviation and power across the operating range of the radio.
It is a very good idea to go thru the alignment program, and write down that information.
Then get the info off the crystal and "tuning data" tag.
I think it is best to measure the 9.6 volt ref off the first pin on the interconnect plug.
I have used both the "save tuning data" and "blank tuning data" successfully.
But, I usually start completely from scratch and entirely realign a radio when blanking a board.
It takes way more time, but I usually have plenty of time.
No reason that you have to do that tho.

Thanks PETNRDX

I can see why you need to realign IF you are using a logic board from another radio OR modding from a trunking to conventional radio.

However, I'm just increasing the number of channels (6 to 32) and adding scanning. The radio is already well aligned and hopefully just increasing the number of channels will not upset things!!

When in the Service Menu, do I definately need to go via the BOARD REPLACEMENT - LOGIC BOARD to note down all the tuning values - OR can I just get all the same identical values from the ALIGNMENT screens? I feel I can do "more damage" in the Board Replacement section vs the Alignment section!!!! Especially as I only want the tuning values as a backup given that I plan on Blanking with EXTENDED SAVE TUNING and then F3 Program with tuning data (not F8). Hopefully I will only need to open up the Maxtrac to read the Xtal labels and measure the P1 voltage if things go wrong !! Is this a correct assumption?

Thanks

Nope, you have to go inside the radio to get the crystal info, and the seven digit tuning.
The seven digit tuning is really a three digit and a four digit.
Unless someone else knows different, You MUST have that, I know you can't get those from the RSS service screens.
That is the only way I have heard of reinitializing the logic board.
I have done it that way a couple hundred times.
The actual ALIGNMENT tuning points you can get from in the RSS service screens.
That ALIGNMENT info is every few MHZ thru the range of the radio for the deviation and the tx power "leveling".
Maybe someone else knows better, but in my experience, the crystal data, the tuning data (hand written tag inside) and the voltage you have to enter manually.
The other alignment points get transferred with the "save old tuning data", I am sure of that.
You are bringing up a really good question here.
For sure if you open the radio and get the crystal numbers, the tuning tag numbers, measure the voltage, AND you have written down the alignment points, you can't foul up the radio.
At least it would take some real misteak to do so.
If you have those numbers you can always put the radio back in the same alignment.

Thanks. I am now 100% clear on the following:

- the only way to obtain the Xtal Ref , Tuning Data Number and voltage is to open the radio and read the labels/measure voltage

However , I am still unclear on the following:

- does the "simple" proceedure which I read about on the Batboard work ie. BLANK using LAB RSS but use "Extended Codeplug , SAVE TUNING DATA" (rather than Clear Tuning Data) and then INITIALIZE also using LAB RSS (Maxtrac High Signaling , Maxtrac 300 , 32ch , scan , Panel 001 etc) and then press F3 (Program with Tuning Data) rather than F8 (Program Radio) ??? It appears that this proceedure saves having to start inputting data

Possible issues with above :

- Does the F3 button exist? I can't see it on the Repeater Builder Screen images - only F8
- Are the Xtal Ref and Tuning Data numbers also "saved" so there is no need to open up the radio?

Thanks

I have another question as well as above questions:

- When I start the BLANKING /INITIALIZATION process , should I have my required OUT OF BAND frequencies already programmed. Are the out of band frequencies used when setting up the "alignment tables" for TX power etc

- OR should I remove all the out of band frequencies because it might confuse the Maxtrac??

- DO I need some IN BAND frequencies programmed so there is not too much "confusion"?

- OR does it not matter one way or the other?

Thanks

I can't remember if it's either 29.7 or 29.6, but anything below that will NOT be properly controlled by RSS or alignment as far as power output and deviation. Each radio is different however, so check it out, you may be OK. Otherwise it may put out way too much power and you will have to put in a manual power pot.

It does not matter what is programmed into memories when blanking.

I always use lab to blank AND initialize if you want to SAVE tuning. I was never sure if the data was either "not cleared" in the radio, or it saved it in RSS because when you go to initialize, there is the F3 PROGRAM WITH OLD TUNING DATA choice. If you switch programs, that would be lost if in RSS.

I would go thru the board replacement steps and write them down anyway if you are not set up to redo everything. And you might look at the stickers first too, sometimes the tuning one is illegible or missing.

Thanks Max-trac

OK , so you need to use LAB to both BLANK and INITIALIZE if you want to use the "easy" method which saves all the tuning data.

Just to be clear, I assume that using LAB to both BLANK and INITIALIZE (rather than using regular RSS to initialize) also saves the Crystal Reference and Tuning Data number and voltage measurement, so there is no need to open the radio to find the labels?

I also read about the TX power issue below 29.6MHz although mike m said that Blanking and Initializing did maintain the out of band power level at 60W - so as you say , maybe it varies from radio to radio.

Could using LAB to BOTH BLANK and INITIALIZE cause any weird effects -such as the flat out TX power below 29.6MHz?

It was also mentioned that LAB RSS did not contain the full Maxtrac model list - will this be an issue with a 6 channel 29.7MHz 60W Maxtrac and the 32ch/scanning mod? Maybe its only an issue with 900MHz radios so thats why all the Repeater Builder articles use the regular RSS to INITIALIZE?

Does the lastest Maxtrac LAB have a full model list? I will be using version R05.30.00 dated August 1991 compared to the regular RSS version R07.02.00a dated Jun 1997.

Are there any other risks in using LAB to both BLANK and INITIALIZE? It appears a much easier way if all the tuning data is saved!!

I saw mention of a Maxtrac SuperLAB dated 19 Feb 1997 - does this actually exist? Has anybody used it? Should I try to use the SuperLAB dated 19 Feb 1997 rather than version R05.30.00 dated Aug 1991?

Lots of questions - maybe I should just open the Maxtrac and look for the labels !!!!!! hi hi

Thanks

i have done the 6 channel limited board to 32 channel full function 16 pin board conversion on a uhf maxtrac and i needed the lab to blank and the standard rss to initialize. the lab would not recognize my radio as a supported model where the standard rss gave me the option of multiple models to select from. it was fairly easy to do. my logic board came out of a maxtrac LS 800 mhz unit and the only thing done to it was a change of firmware chip.

Thanks kb2crk - I wonder what version of LAB you used? Maybe it was a very early version? I will be using version R05.30.00 dated Aug 1991.

Anybody else have any feedback on any of the above questions?

I'm about to do some TX testing on various freqs using just the 6 channels - then I will start on the 32 channel mod.

I've put together a 10m vertical and noticed lots of QRM - I used an AM comms receiver to "hear" the QRM. My 80m dipole is much much quieter and although not resonant on 10m can receive weak signals which are masked by the QRM on the 10m vertical. So I need to add some DFing to the "to do" list !!!!

Thanks

I have now done some TX testing with weird results!!!

Into a dummy load (SWR 1.1to 1) , I am getting around 60 - 75W between 27.8 - 31MHz

Into a vertical antenna (SWR 1.5 to 1 @ 29.6MHz) , I am getting between 70 - 90W between 27.8 - 31MHz

Results are outlined below:

27.8MHz : 60W dummy load ; 70W vertical antenna
29.6MHz : 65W dummy load ; 80W vertical antenna
29.7MHz : 65W dummy load ; 80W vertical antenna
29.8MHz : 60W dummy load ; 85W vertical antenna
30.0MHz : 70W dummy load ; 90W vertical antenna
31.0MHz : 75W dummy load ; 50W vertical antenna

A higher SWR on the vertical seems to result in more TX power - you would expect less!!! Although power drops off at 31MHz on the vertical (but rises on the dummy load)

I also got a small RF burn on my finger from the metal hook on the back of the mic - a real "all black" GM300 type - must have been too much RF floating around !!!

Anybody any ideas?

I also checked out the ALIGNMENT section of the SERVICE MENU - ie. NOT the Board Replacement section.

The Alignment section is NOT a repeat of the Board Replacement values - it just provides ONE relative value for TX Power Adj , Dev Adj and Ref Warp Osc NOT 16 separate values on different freqs. So using the Alignment section is NOT a "safer" alternative for extracting all the tuning data - you need to go into the Board Replacement section.

I guess the Aligment section TX Power Adj lowers ALL 16 data points by the same proportion. Maybe this is a better way to lower the TX power rather than adjusting all 16 tuning values in the Board Replacement section?? Presumably , you set ALL TX power data points in the Board Replacement section to 60W and then use the Alignment section to lower the TX output on all freqs to , say , 50W???

Yes seen it many times with a reactive vertical antenna with moderate RF floating on the coax line and poor grounding which equates to you getting a good RF burn on your finger.

As to the higher power reading under high VSWR, Basically the directivity of your RF power meter is degrading under even moderate VSWR.

What type of RF power meter are you using ?


Mike

My power meter is a Diamond - sadly not a Bird - but its normally OK even upto 23cms. Maybe there was too much RF floating about - the antenna was in doors !!!

I will try my Welz meter to see if there is any difference.

I've decided to first test the TX power output with JUST IN BAND freqs to compare the output with OUT OF BAND freqs.

Any more comments on all the above questions?

I think I will open up the Maxtrac and obtain all the sticker info. I will then try the "simple" LAB RSS ONLY for BLANKING and INITIALIZING and if that does not work (maybe due to a limited list of models in LAB RSS), I can immediately switch to the regular RSS - does this make sense?

I have now checked TX power output with just IN BAND freqs running into a dummy load:

30MHz - 70W
31MHz - 80W
32MHz - 80W
33MHz - 80W
34MHz - 75W
35MHz - 80W

When I used the Welz meter (rather than the Diamond), the TX power output was about 10W less!!!!! I guess the spec of both meters is +/- 20% or worse hi hi

I have also extracted the BOARD REPLACEMENT values which was very easy and not as "dangerous" as I was expecting - just remember to press F10 to move onto the next section so NO changes are made (DO NOT use F8 which saves any changes)

The 16 separate TX Power Calibration values started at 112 , increased to 117 and then back to 111.

The TX dev calibration started at 47 and slowly decreased to 21

The TX Power Adjust and Warp Freq Adjust were IDENTICAL to the values in the ALIGNMENT section of the Service Menu.

I think I will leave the 16 separate TX Power Calibration values the same and just adjust TX power using the TX Power Adj (value of 111) which I guess acts as a proportional TX power adjuster ??

Next step is to open up the Maxtrac and extract the Xtal Ref and Tuning data and voltage measurement.

I've been trying to download the pdf file from the Repeater Builder site which outlines the Maxtrac dissassembly instructions but it keeps stopping at page 23 - maybe its my old version of pdf or the file is corrupt?

"I've been trying to download the pdf file from the Repeater Builder site which outlines the Maxtrac dissassembly instructions but it keeps stopping at page 23 - maybe its my old version of pdf or the file is corrupt?"

I just downloaded all four parts of the MaxTrac manual; no problems found. I was able to page through each section from beginning to end using the current version of Adobe Acrobat Reader.

Bob M.

Thanks kcbooboo

Is there a "timeout" on the Repeater Builder site. I'm using dial up and the required pdf file is "large" in dial up terms - about 17MB I think - which takes about an 1 hour to download. Does the Repeater Builder site let you download for 1 hour? I've tried 3 times.

I had no problems downloading a 4MB file.

"Is there a "timeout" on the Repeater Builder site. I'm using dial up and the required pdf file is "large" in dial up terms - about 17MB I think - which takes about an 1 hour to download. Does the Repeater Builder site let you download for 1 hour? I've tried 3 times."

None that I'm aware of.

I've extracted the disassembly section (last 7 pages from part 4 of the manual set) and posted it separately as a 1.5MB file:

http://www.repeater-builder.com/maxtrac ... disass.pdf

This will be deleted in 24 hours.

Bob M.

Thanks kcbooboo . I downloaded the 1.5MB pdf file with no problems at all.

I guess somewhere along the line there must be a timeout issue - maybe my ISP provider with pdf files?? Alhough I can stay online for hours with usually no problems although sometimes I need to redial for no reason. As I say, I did try 3 times with the 17MB file so I doubt it was just a random dropout - but who knows - anyway many thanks again for the "dial up friendly" size file!!!

I THINK I have successfully managed to both BLANK and INITIALIZE my Maxtrac into a 32 channel/scanning radio using just LAB RSS and did NOT need to input ANY tuning data - everything was carried over using "F3 Program with old Tune Data".

What I DO NOT KNOW is if the Crystal Data, Tuning Data and Measured Voltage was carried over OR whether default values were automatically used - any thoughts???

I DID disassemble the radio and have extracted the Crystal Data, Tuning Data and Measured Voltage so I can always add back the original values if necessary.

All the other tuning values were identical when I used BOARD REPLACEMENT to just view (F10) rather than save (F8). I used LAB RSS to view - maybe it would have been better to use regular RSS??

The LAB RSS version R05.30.00 DID contain a 32 channel 29.7-36MHz scanning model listing (D51MJA9DA5_K).

TX power output on IN BAND freqs into a dummy load both BEFORE and AFTER the 32 channels mod were basically the same between 30-36MHz (ie. around 75/80W)

I used the TX Power Adjust feature (1 value) in the ALIGNMENT section (NOT the Board Replacement section) of the Service Menu to lower the power across all frequencies. The original value was 111. The RSS Test Freq is 32.75 MHz. I got the following TX output for different values into a dummy load:

111=80W (using the Diamond meter!!!)
100= 60W
90=50W
80=40W

I set the TX Power Adjust to 90 (ie 50W) and got the following IN and OUT OF BAND data after reprogramming the radio using regular RSS - also note that using the vertical (rather than dummy load) now results in broadly sensible TX power/SWR figures , as follows:

27.8 MHz - 50W dummy load ; 40W vertical (SWR 1.5:1)
29.6 MHz - 52W dummy load ; 40W vertical (SWR 1.9 :1)
29.7 MHz - 52W dummy load ; 46W vertical (SWR 2.0:1)
32.0 MHz - 50W dummy load ; 35W vertical (SWR 3.5:1 ie very high)

It looks like the original high (80W) RF power was affecting my Diamond meter!!!! (as mike m said).

Current consumption is now around 10A ; originally it was around 15A (just using meter on PSU)

I noticed that the radio is now about 100Hz off freq (which is OK) although I think it was origianlly spot on!!! BUT I had NOT fully fitted the metal screening can - I want to get the SQ set correct.

Here are a few additional comments:

- when you dismantle the radio , you need to remove the side screws for BOTH the top and bottom covers - you only need to remove the top cover to obtain the tuning data BUT the covers have tabs which both sets of screws pass through. You also need to remove the front panel screws.

- I used my "expensive" Fluke 87 III meter to measure the Voltage at 9.67v (although I did not use it). My "cheap" meter measured P1 at 9.64v - it got me wondering what is the effect of using different voltage values due to meter inaccuracies??

- the Crystal Data value was 3310 1767

- the Tuning Data value was 285 3392

- The Tuning Data sticker was on the 24 pin IF/mixer IC NOT inside the screened can.

- The front end tuning cans are "empty" ie. no ferrite/brass slugs (like 6m Maxtracs)

I have another question - does the Crystal Data , Tuning Data and Measured Voltage effect RX front end sensitivity?? Or is it just to do with TX power and the Ref Osc??

The next step is to program all the required freqs and do some RX sensitivity checks.

I have a PROBLEM!!! Intermitant TX.

The Maxtrac was working perfect then I lost TX. Instead of a constant carrier, I was getting a chuffing carrier putting out milliWatts - too low to move the meter. Current fell from around 10A to less than 1A.

I initially thought it was:
- TX VCO but same problem on 31MHz ie. IN BAND..and TX had been working perfect down to 27.8MHz
- top metal screening not fitted properly and causing instability.

Infact , when I pushed the screening completely into place , I started to get TX output and actually managed to have a QSO for a few minutes until the problem returned.

Maybe its just a problem with the antenna or power/swr meter. Could be a poor coaxial connection (although RX seems to be OK) and Maxtrac is closing down TX?? BUT I don't get a TX power "spike" on the meter which you would expect before power is backed off??

TX has now returned and I'm now getting 50W at 29.6MHz into the vertical rather than the previous 40W ..but same 52W into the dummy load.

Any thoughts?? Maybe its a Xtal Ref/Tuning data issue??

With the 10m Maxtrac, RX sensitivity is OK at 29.6MHz although sensitivity does fall when you RX about 2 MHz lower.

I am aware that for 6m Maxtracs, you need to add brass screws (as per Repeater Builder info) to improve RX sensitivity when you INCREASE the frequency ie. operate 4 MHz higher than normal.

I was reading some feedback from a question I asked a few years ago about UHF GM300's and lowering the RX from 438 to 433MHz AND maintaining RX sensitivity.

I was told the following:

- add BRASS or ALUMINIUM cores to lower the inductance and RAISE the frequency (ie. on a 6m Maxtrac to optimise at 54MHz??)

BUT

- add POWDERED IRON cores to increase the inductance and LOWER the frequency (ie. on a 10m Maxtrac to optimise RX below 29 MHz??)

Any thoughts?

UPDATE: 15 months on and I have finally got round to building a full size 10m dipole to fully test out the 10m Maxtrac.

I have NOT yet inputted the extracted Xtal Ref, Tuning data and P1 voltage measure - all I have done is use LAB RSS to BOTH Blank and Initialize. Given my Maxtracs apparant TX instability, I was expecting to have to input the values using regular RSS...but I thought I would wait until the problem reappeared.

When I first tested the dipole, I was again getting the weird high TX values (80/90w) and high SWR. I'm certain that this was due to too much RF floating on the coax. The solution was to build a very simple UGLY BALUN. This is just 18-21 ft of coax wound on a old 4 inch plastic drink bottle. The diameter is not important , just the length of coax...although I only used 17 ft as I had a ready made Belden coax patch cable. I connected the balun about 6 ft from the dipole T junction. There is some useful info on the web about Ugly Baluns. There is also some debate about whether you need 18-21 ft for 10m..some say you only need 6-7ft for 10m. Anyway, it seems to WORK..I now have an SWR of 1.5 at 29.6MHz , 1.1 at 29.3MHz and 1.8 at 28Mhz and around 50W output across the band.

The TX instability has not yet reappeared and I have not had any RF burns!!! ...although I will probably eventually use regular RSS to input the original XTal Ref, Tuning date and voltage measures. I think just using LAB to both Blank and Initialize results in DEFAULT values being used so alignment is not spot on - TX is about 100Hz high compared to the original setting but thats OK.

Anyway, I have just worked 6000 miles into Brazil...which is 5950 miles further than I expect to work on a Motorola!!!!! I've also worked into Italy!!!

UPDATE: 20 months on and I have finally worked "across the pond" using my MaxTrac!!!

I worked WB9OWN, Dave in Wisconsin who interestingly was using a GE Ranger and WD4HEM, Rusty in South Carolina.