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Maxtrac Filters Becoming Unobtanium

This forum is for the discussions targeted at converting various models of Motorola equipment to operate in the 900MHz Amateur Band.

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W6JK
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Maxtrac Filters Becoming Unobtanium

Postby W6JK » Tue Mar 04, 2008 10:40 am

It looks like supplies of the Toko filters we've been using in our Maxtrac conversions are drying up. Both of my suppliers are completely out of them, and there are three of us that I know of with small personal supplies remaining. When Bob, Derek and I are out of them the only source may be from people who bought small quantities from one of us and never used them. I'll be selling mine on eBay soon, with a note in FSWT when they're ready.

Jeff W6JK

ke2n
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Re: Maxtrac Filters alternatives

Postby ke2n » Fri May 23, 2008 4:59 am

I wonder if one of the new SMT filter could be stuck onto a little piece of PBC with 50 ohm striplines and two pins sticking out in just the right places.

this one is available from Mouser for $1.41 in single-unit quantities

http://www.rfm.com/products/data/sf2049e.pdf

anyone want to try?


Ken

wa6jbd
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Re: Maxtrac Filters Becoming Unobtanium

Postby wa6jbd » Mon May 26, 2008 8:56 pm

Has anyone tried retuning them? How does construction compare to, say, a Spectra filter? I've had a great deal of repeatable success retuning those.

WB6DGN
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Re: Maxtrac Filters Becoming Unobtanium

Postby WB6DGN » Tue May 27, 2008 12:57 am

I wonder if one of the new SMT filter could be stuck onto a little piece of PBC


Sure, you could mount the filter to a sub board, then fasten that to the RF board but how are you going to properly "stick" the filter to the sub board without SMT equipment? You would need to pay someone with SMT equipment to do that or risk damage to the filter trying to do it yourself in some makeshift manner. Remember, done properly, using SMT tools, the temperature does not exceed about 450 degrees F, or, maybe, a little less. Also, according to other threads on this topic, you should also consider an active stage on that sub board to make up for the increased loss through that type filter if you are going to do the job right
Are the original Toko and/or Murata filters no longer being manufactured by their respective manufacturers or are the suppliers just not ordering them for stock? Perhaps some enterprising group (or club) could put together an order sufficient to persuade a supplier to reconsider?
Tom

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W6JK
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Re: Maxtrac Filters Becoming Unobtanium

Postby W6JK » Tue May 27, 2008 2:03 pm

With the change from leaded to unleaded, so to speak, has come a change in the minimum order from 100 to 1000 pieces. That's enough to flood the market for quite some time, so there's little hope of recovering the investment any time soon. However you cut it, someone(s) would have considerable funds tied up for quite a while.


'JK

wa6jbd
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Re: Maxtrac Filters Becoming Unobtanium

Postby wa6jbd » Thu May 29, 2008 5:49 pm

A little research in the Mouser catalog shows some Toko Helical filters that look promising. If they're tunable, it's conceivable that the could be tuned such that the roll off starts in a portion of the band that could allow even more rejection of 929 paging than the previously used ceramic filters have provided. I looked at Murata and Toko's web pages, and didn't see the previously used replacement filters listed, so it appears it's a manufacturer issue, not a distributor issue.

Those 915 MHz smt SAW filters are probably quite usable . SMT techniques are not nearly as difficult as they would first appear, and professional results can be had with, believe it or not, a standard soldering iron. The microwavers do it all the time.

In the meantime, my Maxtrac's have arrived from eBay. I intend to determine the feasibility of retuning the existing filters.

wa6jbd
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Re: Maxtrac Filters Becoming Unobtanium

Postby wa6jbd » Thu May 29, 2008 9:22 pm

Update on the Maxtrac filters... there's good news and bad news. The good news is, they CAN be retuned. The original FDK filters are tuned by filing or grinding down the end posts, where the input and output terminals are. Access is through the top, under the label, which must be removed. The bad news is, they can only be moved up in frequency. This would bode well for anyone trying to convert an 800 MHz radio to 902 for a repeater receiver, but doesn't help in the case trying to bring a 900 radio down in frequency. Well, it was a good thought anyway... =)

mike m
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Re: Maxtrac Filters Becoming Unobtanium

Postby mike m » Fri May 30, 2008 8:58 am

http://dkc3.digikey.com/PDF/T082/1349-1350.pdf


Why make things so hard ?

Go to digikey and get some of the above Epcos 915 MHz saw filters.

Even in small Qty the price is right, just 1 buck 47cents for singles.

I use the above in my MPA handhelds and in my Maxtrac mobile.

Make up a small sub PWB and get some small lengths of mini coax, RG-174 works fine for 1 inch pigtails, and solder them into the existing filter space.


M

wa6jbd
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Re: Maxtrac Filters Becoming Unobtanium

Postby wa6jbd » Fri May 30, 2008 9:05 pm

Why make things so hard?

Because I can, mostly. =)

I have access to the test equipment to at least attempt to retune filters, so it's not something extraordinarily difficult. Any chance I can take to use a multi-kilobuck network analyzer to save a $1.47, I will.

The SAW filters are a good replacement, though, so the lack of the previous model is not an unsurmountable loss.

WB6DGN
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Re: Maxtrac Filters Becoming Unobtanium

Postby WB6DGN » Sat Jun 07, 2008 6:31 pm

Those 915 MHz smt SAW filters are probably quite usable . SMT techniques are not nearly as difficult as they would first appear, and professional results can be had with, believe it or not, a standard soldering iron. The microwavers do it all the time.


I know it can be done; one of the guys I worked with insisted on using his soldering iron rather than the SMT equipment we had available, but "professional results"? I'll be one of the first to sign up for lessons (seriously!). How do you deal with a component whose contacts are completely hidden underneath the part? I've seen guys use heat guns, too. They work, but for how long?

The microwavers do it all the time


Wasn't there a song by Mariah Carey about that?


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