Kenwood TM-V71a and EME on 70cm.

Discussion in 'Satellite and Space Communications' started by W8MWR, Feb 6, 2017.

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  1. W8MWR

    W8MWR Ham Member QRZ Page

    I just bought a Kenwood TM-V71A in the American ("K") version. The unit is spec'd as TX at 438 ~ 450 MHz. The US Band Plan for 70cm lists EME as 432.00-432.07MHz, the 70-cm calling frequency is 432.10, and 435-438MHz as Satellite only (internationally)! Even the "E" and "M4" versions start at 430MHz, loosing 10MHz at the start of the band. WTH? I know I can have the "MARS/CAP Mod" performed but I really want to know what the deal is with this. Why make a true cross band rig that cuts out 18MHz of the most useful frequencies?
  2. WD9EWK

    WD9EWK Ham Member QRZ Page

    Because most FM operating on the 70cm band in the Americas is above 440 MHz. The main exception to that is FM satellite operating, which would occur at 435.438 MHz. Besides EME and general weak-signal (non-FM) operating, the spectrum below 440 MHz is also used for repeater linking and amateur television, among possibly other uses.

    FM is not normally used for EME work, because of the power that would be needed to make an FM signal bounce off the moon and be readable to any degree back on the ground. This is why narrow-bandwidth modes like the WSJT modes, CW, and SSB are preferred for EME. WSJT is especially preferred for the smaller stations trying to work EME.

    The calling frequency for EME is at 432.100 MHz, in CW or SSB - not FM.

    Last edited: Feb 6, 2017
  3. AD5KO

    AD5KO Ham Member QRZ Page

    That does not sound right, unless this image is meant to misslead people. Here is an image off the kenwood site.. Notice the push to talk is Highlighted on 435.000

    Specs :
    Frequency Range
    Band A & B TX
    144- 148 MHz
    430 - 450 MHz

    So according to Kenwood USA your information is incorrect.

  4. WD9EWK

    WD9EWK Ham Member QRZ Page

    I saw what W8MWR listed in both PDF manuals for the TM-V71A, which I just downloaded from the Kenwood web site.

    The 438-450 MHz range for the 70cm band was commonly used by Kenwood in its amateur gear until the late 90s or early 2000s, then they went with at least 430-450 or maybe 420-450 MHz for the range their radios would transmit across. I know my TH-D72A and TH-D74A will transmit down to 430 MHz, and will have to check tonight if they transmit down to 420 MHz unmodified.

    By the way, the screenshots appear to show something using the radio(s) in Europe. The 144.800 MHz frequency is commonly used for APRS over there, and the European-spec radios would transmit on the 70cm band at 430-440 MHz only. Also note the German call sign above the VHF frequency in both screenshots (DF0TK).

  5. AD5KO

    AD5KO Ham Member QRZ Page

    Yes, I see that EU APRS frequency now you mention it. Good catch.

    But the Specs I posted are off the Kenwood USA page. So according to Kenwood USA the radio should TX on 430 Mhz.

    I have been looking at getting a mobile for Sats and I would be really annoyed if I purchased that radio and was a victim of that deception. I have considered that radio too.
  6. WD9EWK

    WD9EWK Ham Member QRZ Page

    At least one of the manuals has the following line:

    "Specifications are subject to change without notice due to advancements in technology."

    I don't own the TM-V71A (nor the TM-D710A/GA - both use the same radio "box"), so I can't test for myself. Seems like the mobiles would be set up like the HTs, transmitting down to at least 430 MHz even in the K version sold in the Americas.
  7. AD5KO

    AD5KO Ham Member QRZ Page

    You would certainly think so.
  8. W5SAT

    W5SAT Ham Member QRZ Page

    My TM-V71A has been modded but I am quite certain it was 430 to 450 Mhz when it was stock. It's roughly 420 to 470 Mhz now.
  9. WD9EWK

    WD9EWK Ham Member QRZ Page

    That's what I thought Kenwood did for almost all of these VHF/UHF FM transceivers for the past decade or so. Allowing 430-450 MHz means the radios can be used by those who travel outside the Americas, or at a minimum outside the USA and Canada, and not have to modify the radios to operate on repeaters in the 430-440 MHz range (something I've done in the past, in Mexico and Australia).

    Both my TH-D72A and TH-D74A HTs will transmit at 430.000-449.995 MHz. If I tune down to 429.995 MHz or up to 450.000 MHz on either radio, they won't transmit.

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