Power Output Kenwood TM-V71A With MARS/CAP MOD

Discussion in 'VHF/UHF - 50Mhz and Beyond' started by KN4DMZ, Sep 5, 2017.

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  1. KN4DMZ

    KN4DMZ Ham Member QRZ Page

    First of all, let's leave out the comments about out of band legality, and why to do it. When you work with FEMA and first responders during a serious emergency, which some of us to, you do not question why this capability should be present -- just in case.

    So that being said, I would like to know that it works relatively well should I ever need that during the next hurricane or other emergency.

    I am looking into the Kenwood TM-V71A with the MARS/CAP mod that GigaParts will do for a new radio.

    I was chatting with a Tech who told me that the power drops off on either side of the ham bands, which I fully expect. What he said that did not make sense what that the power would be at or close to Zero at the extreme ends of the opened frequencies.

    This power drop sounds extreme and I have tested Chinese radios into a dummy load and they do not drop off this much out of band. Now the Chinese radios have all sorts of other problems so I the idea of a quality ham rig with this capability is of great interest.

    I have thought about the Alnico dual band which is Part 90 certified, but again I have heard mixed reports about quality on that radio.

    Since have seen at least one of these units for sale on QRZ with the mod and a string or two on the subject, surely someone that reads this forum has this mod and can test the power either on the Kenwood or another radio with the MARS/CAP mod. I would love any input that any of you have on this subject.
    AA5AZ likes this.
  2. WA4ILH

    WA4ILH Subscriber QRZ Page

    How far out of the ham band do you consider operating. Transmiting into a dummy load is not the same as transmitting into an antenna, which has a narrow bandwidth.
    Tom WA4ILH
  3. KN4DMZ

    KN4DMZ Ham Member QRZ Page


    Thanks for the reply.

    I totally understand the antenna SWR issues and have done tests on both a Diamond X50 base antenna and a Comet SBB-5NMO mobile antenna. In both cases SWR was bit below 2:1 when in the 158MHz region which is acceptable but not optimal and slightly better on UHF around 469Mhz.

    For purposes in my area, I would not expect to go much higher than 159Mhz on VHF or 469Mhz on UHF. Also this would only be under special, emergency situations, particularly when working on the DHS/FEMA interopability channels.
    Last edited: Sep 6, 2017
  4. WA9SVD

    WA9SVD Ham Member QRZ Page

    Well, for one thing, there IS no longer a MARS/CAP mod for ANY amateur equipment. Many years ago, CAP REQUIRED certificated equipment (by FCC) for use in their service, so NO amateur equipment was allowed or accepted.. THAT only allows for MARS operation, and your authorized MARS authorities will give you the proper modification info; most manufacturers will also give you the proper mod info for make/model/revision upon receipt of your official MARS license and authorization as a legitimate MARS affiliated station.
    Most Amateur equipment just does NOT meet the frequency stability or accuracy required by CAP. And most Amateur equipment is designed ONLY to operate within very specific frequencies, such as 144-148 MHz, or 440-450 MHz (FM) and will have (often very) degraded performance outside the Amateur bands.
    I'd strongly SUGGEST using commercial gear (obtained BEFOREHAND) for use outside the Amateur frequencies, at least for transmitting, and only on bands for which you are permitted.
    KC9VFO and WD9EWK like this.
  5. K9STH

    K9STH Ham Member QRZ Page


    You are treading on thin ice using a modified amateur radio unit on frequencies where certificated equipment is required. If caught, you can be subject to penalties including

    Fines up to $11,000 per day per unit used.

    Confiscation of the equipment.

    Loss of your amateur radio operator's license and not being allowed to get another for the rest of your life.

    In certain situations, being sent to jail!

    Since you have an amateur radio operator's license, the FCC will "come down" harder on you as compared to someone who does not have a license. You signified, by signing your application for an amateur radio operator's license, that you know, and will obey, all regulations concerning operation of radio equipment and not just amateur radio equipment!

    There are several Chinese portables that do have certification for use on 47 CFR Part 90 frequencies that are available for under $50.00. Those units can also have amateur radio frequencies installed. It is perfectly legal for a licensed amateur radio operator to own, and use, such radios on both amateur radio frequencies and on commercial two-way frequencies when authorized. If it were me, I would obtain one of these radios (I actually do own one but only use it on amateur radio frequencies) to be completely safe where the FCC is concerned.

    When working with a Federal agency, the ice is even thinner because those agencies are often going to verify the equipment being used with their operations.

    It is actually against the "rules of the road" here on QRZ.com to give information on how to modify amateur radio equipment for use on frequencies outside of the amateur radio bands. The exception to this is for supplying information to use equipment on the 60-meter band when that band has not been included originally.

    Glen, K9STH
    K3UJ and WD9EWK like this.
  6. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page


    When all else fails, use the equipment that's supposed to be used.
  7. WG7X

    WG7X Platinum Subscriber Platinum Subscriber QRZ Page

    When a post begins like this, it usually does not survive long. We, as a group, usually obey the rules and regulations governing our service and other services as well.

    Glen has outlined it very well already.
    KA0HCP and WD9EWK like this.
  8. WA9SVD

    WA9SVD Ham Member QRZ Page

    Thanks, Glen. Well said, better than I.
    Last edited: Sep 10, 2017
  9. KN4DMZ

    KN4DMZ Ham Member QRZ Page

    All well understood. I did not intend to stir up a behive.

    I had planned to buy a part 90 approved radio as the most of the frequencies needed are in the commercial pool,

    but I wanted this as backup in an emergency because I love those Kenwood as a ham rig.

    It is a mute point because the radio can't cover the chan neon spacing required anyway.

    My ideal solution is to buy a part 90 approved rado that has the capability to cover ham.

    Not many options in a dual band---looking at Alonso which seems to do this.
  10. WA9SVD

    WA9SVD Ham Member QRZ Page

    Look at the "brite side." If you have a Part 90 radio, you usually CAN also program it for Amateur frequencies, even repeaters, and you will usually have a more reliable, more trustworthy radio!

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