low band maratrac to 6 meter ham

[kb2crk]

just a quick question. is the low band maratrac programable to the 6 meter ham band and will it lose any power being used there.
i have found conflicting information on this and was hoping to get a definitive answer here

thanks paul

[Pj]

When in doubt, Batlabs.com

http://www.batlabs.com/maratrac.html

[kb2crk]

this is what i found

Modifications for Effective 6meter Use

Some information regarding moving the Maratrac out of band (50 to 54 mhz):

The Maratrac is a real bear to modify for amateur use. Its front end is designed for 42 to 50, and that's about it. Above 50, it rolls off very steep and is useless in the FM portion of the band. Also neither the transmit or receive VCOs will lock reliably much above 51 so you'll need to change out the coils (available from Digikey). Fortunately, the injection oscillator, exciter, and power amplifier are pretty flat and you won't need to make any changes there. The one nice thing is that the only physical modifications that are needed are all on the RF board. You don't have to hack the radio apart. You can install a stock RF board and return the radio to stock condition. With the modified board, your radio will now operate from about 46 to 54 MHz and you'll lose the 42 to 46 MHz sensitivity (if you can lock the VCOs)

In addition to the VCO coils, you'll need to make extensive modifications to the RF board (like changing out 20 or so chip capacitors). Its a good idea to sweep the entire front end before making the changes to try and shift the front-end curve up by 4 MHz. When you finish, if you're lucky, the sensitivity should be about spec. (0.35uV for 12 dB SINAD).

It's a nice radio but a lot of work to convert, not to mention the need for the software that will allow you to program it out of band.

The bottom line is that, unless you like spending few bucks on parts and several nights working under a magnifying glass, stick with the crystal bound radios - this one wasn't designed for amateur use.

Update:

After programming up the radio out of band, you should be able to tune up the RF board the same way you do the low band Maxtrac using the SL point. More than 10 of these have been done using this technique and it works without a flaw. There is no need to change any parts on the board unless you want it broad-banded. Maratracs have been made to TX and RX as high as 56 MHz without loosing any power.

So, what have you got to lose? Give it a try.

it says it cant be modified easily but then says it doesn't need mods.
i was hoping to find out if it had been done and if it works.
thanks again
paul

[Pj]

We the admins do not have access to that part of the site. The person who actually has control went MIA awhile ago.

Reading that section, do the RSS programming mods, then just tune the radio as you would normally for the new sections of the band you want to play with.

Orginally before that was discovered, there was some hardware changes needed. Many people sucessfully did that hardware mod...until someone said "hey, what if we just retune the radio?"

If you want a high powered radio to do 6M, the lowband X9000 is the way to go. 32 or 64 channels, locate the HAM RSS and your good to go. That was most likely the BEST broadband lowband radio ever built. I've used it from 27 to 54 without a problem. The HAM RSS lets you do 25-56 IIRC.

[kb2crk]

thank you for the info.
i will have to do a little more research

[kcbooboo]

I'm using one at home and had no output power issues at all. It seems to be a lot better than the low-band MaxTrac in that regard.

Easy to convert. Google for:

maratrac quick

and note my avatar.

Bob M.

[motorola_otaku]

Easy to convert. Google for:

maratrac quick

and note my avatar.

Bob M.

He posted the same question on Hamsexy. I pointed him in the same direction.

Short version is that you use the same mod as the lowband Maxtrac to get the VCO to lock, then you drop brass slugs into the coils on the RF board to peak RX sensitivity. It's a piece of cake.. if you have access to a service monitor or other calibrated RF generator. And the finished product has a damn hot receiver.

[Will]

motorola_otaku,

Do you have a source for the brass slugs? I had to make mine, very time consuming.

[kb2crk]

thank you all for the help.
i will be trying to catch one of the maratracs cheap if i can.
i should have my uhf maxtrac by the end of this week.

[kc7gr]

You don't have to use brass, Will. I've found that stainless steel hex-socket set-screws work very well indeed, and they're readily available at larger hardware stores. 6-32 should be the correct diameter.

The trick is not so much the screw as making sure the material is non-ferrous (or, to put it more simply, not magnetic). Inserting such in a tuning coil has the reverse effect of, say, a ferrite slug by actually decreasing inductance.

Happy tweaking.

[kcbooboo]

I've had great luck using #6-32 brass machine screws that I buy at my local Home Depot. They come as a bag of 6 screws for $0.99. Unfortunately you need 8 per radio, so you don't break even until you buy 4 bags and do 3 radios.

I started with 1/2 inch long round-head slotted screws that I cut down (with one of those multi-purpose stripping/crimping tools) to just over 1/4 inch of thread under the head. These can be inserted all the way into the receiver front end coils on MaxTracs, but they stick up just a bit too far for MaraTracs. A friend used flat-head screws and they don't stick up quite as far as the round-head ones.

Alternatively, #6-32 by 1/4 inch brass or stainless-steel set screws - if you can find them - would be perfect.

Just make sure they're really brass and not just brass-plated, or stainless-steel. Some marine stores will have brass or even bronze hardware as well, but be prepared to pay big bucks there.

Bob M.

[motorola_otaku]

I had to make mine, very time consuming.

Heh, that's what we did too.. cut off and de-burred pieces of brass welding rod.

[kb2crk]

time to find some brass screws. the radio is programed and just waiting for the final touches.

[PETNRDX]

I have posted similar replies to this question before, but will comment again anyway.
I modified several of these many years ago, and it makes a great 6 m radio.
Using some brass, bronze or SS rods or screws works OK.
If you grind the rods down much to smaller diameter than the slug hole, you can put shrink tube over
short (about 3/8") chunks of of the metal. The piece of heat shrink tube should be longer by
a half inch or so.
After a couple of tries you can make the rod/tube combination slip in the slug hole with
just enuf friction to stay in place while tuning.
The tuning is usually very broad.
Once you get it tune this way, carefully fold the heat shrink tube over tape in place and put the
shield cover on. It holds the metal slug in place enuf to use the radio just fine.
This is a pretty crude way to do it, but it will allow you use the radio and verify that it
is worth spending more time on to make it better later.
I ran a couple of them like that for YEARS. (and I have a Maxtrac here is the shack done that way)
All that said, it really is better to remove the offending coils and shorten them by one turn,
or just remove the coil, short the uppermost two turns with a blob of solder, and re-install.
I used a A7 in my 4X4 veh that was driven to all the lower 48 states at one time or other and it was a great radio.
It got replaced a few years ago with a X9000.
The Maratrac is in a box in the garage, but it is going in YF's car this spring.

[kb2crk]

i have been working on this when i have had time and i now have it to the point where it will transmit. ran out of time to tweak it and fully align it though. i used 5/16 brass hex socket screws as i found a box of 100 on ebay for 5 bucks. i just left them about 1/16 of an inch out of the tops of the coils. i will post again as soon as i have it 100% up and running which i hope will be this weekend.