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    "url": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/V367P22AGL7SCD3XJ275KO2ZFWVCTXB3/?format=api",
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    "message_id": "CAOsf+NSZ7t_YdUsS2qDHBP94Qrj-uc02M=L4OtMhJRYxhZGrnQ@mail.gmail.com",
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    "thread": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/thread/V367P22AGL7SCD3XJ275KO2ZFWVCTXB3/?format=api",
    "sender": {
        "address": "w2hro.fn20 (a) gmail.com",
        "mailman_id": "56ad9360da124e679a8e571628e4a15d",
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    },
    "sender_name": "Paul Andrews",
    "subject": "[AMSAT-BB] Re: UHF preamps",
    "date": "2022-12-28T18:28:07Z",
    "parent": null,
    "children": [
        "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/OKYUJ3JPVLDNMOKCIVX7YGYYUIC4YPNF/?format=api"
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    "content": "The 70cm band is hamonically related to the 2m band.\n\n2m into 70cm 3rd harmonic interference is more likely than 70cm into 2m.\n\nHappy New Year.\n\n73 - Paul - W2HRO\n\nOn Wed, Dec 28, 2022, 10:00 tjschuessler--- via AMSAT-BB <[email protected]>\nwrote:\n\n> I do not believe it is RF from the 2 Meter transmit that is leaking into\n> the antenna side, as I run a duplexer in front of the preamp input.  70 CM\n> portion of arrow through a duplexer with only the 70 cm signal passing\n> through that duplexer.  I do the same on the 2 Meter side.  This\n> arrangement almost totally eliminates any de-sense of the RX on 70 CM from\n> 2 M transmit.\n>\n>\n>\n> *From:* Paul Andrews <[email protected]>\n> *Sent:* Tuesday, December 27, 2022 9:02 AM\n> *To:* [email protected]\n> *Cc:* AMSAT-BB <[email protected]>\n> *Subject:* Re: [AMSAT-BB] UHF preamps\n>\n>\n>\n> Tom,\n>\n>\n>\n> Are you relying on the transmit RF sensing feature of this 432 MHz\n> preamp?    RF sensing can be unreliable.  You might use the FT-847's RF amp\n> enable output to trigger the external preamps.\n>\n>\n>\n> Another thought.   It is possible that your 2m transmit signal is leaking\n> into the input of the 70cm preamp.   It's likely that significant coupling\n> is occurring at the arrow antenna.\n>\n>\n>\n> You might consider using separate preamps and isolating relays.\n>\n>\n>\n> 73 - Paul - W2HRO\n>\n>\n>\n>\n>\n>\n>\n>\n>\n>\n>\n>\n>\n>\n>\n>\n>\n>\n>\n>\n>\n>\n>\n> On Mon, Dec 26, 2022 at 11:32 PM tjschuessler--- via AMSAT-BB <\n> [email protected]> wrote:\n>\n> For my portable/temporary satellite antenna rig, I have need of using a\n> UHF preamp, which I have strapped to the tripod that holds and aims my\n> Arrow antenna.  I find that my FT847 is just not as sensitive on 70 CM as\n> it is on 2M.  I have been using an ARR (Advanced Receiver Research )\n> SP432VDG which is supposed to have a maximum power pass through imitation\n> of 25watts.  I try to be pretty careful as to how much output I run through\n> the thing, maybe limiting to 15 watts or so.  Unfortunately, I have blown\n> the preamp out several times, even with being conscious of the RF level.  I\n> sent the pre to them, they repaired and sent back.  I recently discovered\n> that I had blown my unit again.  Symptom is that it adds noise to the\n> output, but does not amplify any signals coming into it from the antenna.\n> I have sent the unit in to ARR in the past for repair.  This time I am\n> contemplating replacing this one with a more robust device that might be\n> able to handle more RF running through it (RF sensing means you will still\n> hit the device with an instantaneous burst of RF before the internal relays\n> kick in.\n>\n>\n>\n> A friend has confided that he has the higher power version of the ARR\n> Preamps, but has had similar problems with killing the things.  Thus I am\n> in the market for maybe another option.  While I oft times, will stroll\n> over to the antenna tripod, and barrel off the cables going to and from the\n> preamp to bypass completely from the transmit chain, this is kind of a\n> pain, even in a portable situation.\n>\n>\n>\n> I looked at M2s web site and can find a 2 Meter amp, but no 70CM (Might be\n> missing something.  I have heard a lot of good things on the SSB preamps,\n> but the only pace I can see them being sold, is Dolstra in Europe.  Don’t\n> see a US vendor.\n>\n>\n>\n> Looking for suggestions.  I would be interested in buying pre-owned,  if\n> someone had a Preamp that would like a new home.\n>\n>\n>\n> I do have a question for Yaesu FT847 users.  With that radio, you can\n> power a Preamp via the built in Bia- T power inserter, And assume that when\n> this mode is turned on, it cuts the inserted DC to the preamp as the\n> tranciever goes into transmit.  Does this work fast enough to protect, even\n> RF switched preamps?  That might be a good safety measure as I have\n> traditionally used external DC to power my preamps.\n>\n>\n>\n> Wisdom from the cloud here would be much appreciated.\n>\n> .\n>\n> Tom Schuessler, N5HYP\n>\n>\n> -----------------------------------------------------------\n>\n> Sent via AMSAT-BB(a)amsat.org. AMSAT-NA makes this open forum available\n> to all interested persons worldwide without requiring membership. Opinions\n> expressed\n> are solely those of the author, and do not reflect the official views of\n> AMSAT-NA.\n> Acceptable Use and Privacy Policies available at\n> https://www.amsat.org/about-amsat/\n>\n> View archives of this mailing list at\n> https://mailman.amsat.org/hyperkitty/list/[email protected]\n> To unsubscribe send an email to amsat-bb-leave(a)amsat.org\n> Manage all of your AMSAT-NA mailing list preferences at\n> https://mailman.amsat.org\n>\n>\n> -----------------------------------------------------------\n>\n> Sent via AMSAT-BB(a)amsat.org. AMSAT-NA makes this open forum available\n> to all interested persons worldwide without requiring membership. Opinions\n> expressed\n> are solely those of the author, and do not reflect the official views of\n> AMSAT-NA.\n> Acceptable Use and Privacy Policies available at\n> https://www.amsat.org/about-amsat/\n>\n> View archives of this mailing list at\n> https://mailman.amsat.org/hyperkitty/list/[email protected]\n> To unsubscribe send an email to amsat-bb-leave(a)amsat.org\n> Manage all of your AMSAT-NA mailing list preferences at\n> https://mailman.amsat.org\n\n\n",
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