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Show all reviews of the Alinco DR-635
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You can write your own review
of the Alinco DR-635.
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N7ANL
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Rating: 4/5
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Dec 31, 2007 12:27
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Intermod, DV & APRS comments
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Time owned: 0 to 3 months
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This comment string began with a complaint from a new user of the DR635T, who had some troubles getting his Packet/APRS option board to work right for him. Another comment, 3rd down the list, claims to have bought the digital voice module by the same number as the first commenter, and was mistakenly disappointed his DV module won't decode the "commercial" APCO-25 format, even calling it "APCO28". C'mon folks, wake up.
My response here is not a review of the radio, but instead is a review of a few of the comments.
First, there are TWO optional modules for this and the other Alinco mobiles, ONE is a packet/APRS TNC board, and the SECOND is a DV or Digital Voice module. I can not speak for either unit, but am simply pointing out the comments are mixed up here.
As an alternative, hams should know there is an aftermarket (not Alinco's) TNC board that can dropped into the Alinco radios for the packet/APRS TNC feature, which may be a better choice, I don't know. Look for it on QRZ as they have a banner ad at the top of the QRZ page. Maybe it's a better choice for packet/APRS than the stock Alinco board.
The other Alinco option is an Alinco Digital Voice module, which uses a "ham specific" digitized voice decoding format, and it does NOT do the APCO-25 commercial DV format. Would be nice if it did, but these are two different formats in the industry, so that's just how it is. This is not Alinco's fault. Icom & Kenwood's new "DV" radios are also on the ham specific DV format and do not do APCO-25 either.
A point many may not know, is EVERY radio & scanner made which has an APCO-25 DV module in it, pays a high price, a licensed user fee if you will, for the use of this module. This is why all APCO-25 2-way radios, and scanner receivers, are much higher priced.
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Further, there a lot of comments in this thread, both pro & con about the how the Alinco handles "intermod". Intermod is a a tenacious problem in all larger and most small cities & towns. Intermod gets into almost every amateur VHF/UHF radio made, though some are better than others. There are several design issues which cause this problem.
I would not be too hard on Alinco if their radio picks up severe cases of intermod, since most all other brands & models do as well. Think about what is happening here.
You have a TWO band radio, with both receiver sections also being the widest design bandwidth possible, all so you can use the radio to receive ALL the ham & commercial & aircraft freqs you desire.
Further, most you are probably using a dual band antenna on the car or at home, and some of these designed antennas are also as broad-banded as the mfgrs can make them.
Thus what you are doing is INVITING intermod issues. If you substituted a wideband Icom or Kenwood or Yaesu radio and various antennas, you would find pretty much the same problems, slightly more or less.
Fortunately, there are several ways to resolve these intermod issues. If you really have bad intermod issues, get intermod-resistant radios & antennas!
~ Get a narrow bandwidth designed ham-only transceiver. Good examples are the much older mobiles like the Kenwood TW-4000 or 4100 series, the Icom IC-3200A or 3210A, or the Yaesu FT-2700 or 2710H. These are all dual band mobiles which WON'T allow you to modify your radio to monitor much of the adjacent commercial or aircraft spectrum. They were designed to have narrow receivers, as intermod in that era was just beginning to show up big-time in the cities. These older radios won't give you a zillion programmable features, but they will limit intermod to the absolute minimum. A tight receiver is your best bet against intermod invasion in the terrible "intermod alley" areas of the country.
~ The second step is go with two SEPARATE single-band AND narrow bandwidth antennas. If your primary operating area is inside the 2m and 440 ham bands, get a 5/8 wave 2m antenna, and a phased 440 ham band antenna, thus running separate antennas with your dual band radio. Tune each antenna to the center of band portion you actually use. So many of those modern wide-banded & dual-band antennas, whether base or mobile versions, are rather broad by design, again, so you can receive "everything" on them. You asked for that, and so you got it. If you want to eliminate intermod, go with narrower bandwidth antenna designs.
~ The third thing you can do is acquire a narrow bandwidth filter for each of your "problem" bands. Several mfgrs offer single-band (either 2m or 220 or 440) inline filters which will keep your desired working freqs peaked, while knocking down those freqs outside the ham bands. These filters are single band units, so you will need to run one with each band and each separate antenna.
When I read all these complaints against a radio that was "market-desired" and designed to be wide banded, I see a lot of amateurs who haven't thought through the problem yet. When you run into a problem, solve it -- by using equipment that was made to solve it. When you leave the chicken coop gate open overnite, the chickens will get out and the coyotes will get in !
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