Yep, There are several conversions on the RB site for the MVP. They are loosely based on the MII conversions. I haven't done many MVP conversions of any particular band, but the ones I have done have not had any internal desense issues.
Scott Scott Zimmerman Amateur Radio Call N3XCC 474 Barnett Road Boswell, PA 15531 ----- Original Message ----- From: "skipp025" <[EMAIL PROTECTED]> To: <[email protected]> Sent: Friday, February 23, 2007 5:06 PM Subject: [Repeater-Builder] Re: 220 repeater receiver recommendations? (MVP?) > What about the GE MVP Scott..? Would the conversion be available > and similar for the MVP Mobile? > > skipp > >> "Scott Zimmerman" <[EMAIL PROTECTED]> wrote: >> >> With respect to using the GE MII mobile frame for repeater applications: >> >> > 1. Can you say categorically that there is sufficient TX/RX > shielding to prevent any desense at any power level the conversion is > capable of operating? >> >> In my experience, yes. In fact, we have had several repeaters that > the sensitivity actually gets BETTER with the transmitter active. (due > to the correct 50 impedance being applied to the TX port of the > duplexer) The only problems we have had with in-cabinet de-sense go > back to issues with a transmitter multiple getting into a sensitive > spot of the receiver. This is a well known phenomenon on UHF Mastr > II's, but it also happens on converted 220 micors and MII's. I have > been wanting to write up this research for some time. I will try to do > it as soon as I can. >> >> 2. When these converted mobiles operate with reduced TX power, what > happens to the output impedance of the TX? Is it still 50 ohms? If > not, does this affect the physical length of the half wave > interconnect cables often suggested between the TX and an isolator > and/or the cavities? >> >> As others have stated, it may not be *exactly* 50j0, but it's close > enough. Realize that most of the "50 ohm" coax cable actually spec'd > to be 52 ohm nominal!! I would think that the cable being 2 ohms off > would be more detriment than the 50ohm designed output / input > impedance that might move fractions of an ohm in impedance due to > being tuned a few MHz from it's design frequency. If you want to get > that picky, should a PA's output be tuned for 50 ohms when the > frequency is changed from let's say 155.xx to 158.xxx? I would think > that if the designers would have thought the port impedance to be that > critical, they would have made provisions to adjust it. >> >> As far as our 220 modifications go; we use a M57774 power module. We > DO NOT modify/retune the VHF pa to 220. If we did, we might run into > design issues where impedance problems might rare their ugly head. We > just use an off-the-shelf solution that works well. >> >> If not, does this affect the physical length of the half wave > interconnect cables often suggested between the TX and an isolator > and/or the cavities? >> >> 3. If the output of the TX is other than 50 ohms as a result of a > power level change, does it upset the adjustment of the downstream > isolator that has been tuned by a tracking generator? >> >> Can't say. I have no experience. I will defer this question to others. >> >> Scott >> >> Scott Zimmerman >> Amateur Radio Call N3XCC >> 612 Barnett Rd >> Boswell, PA 15531 >> >> ----- Original Message ----- >> From: [EMAIL PROTECTED] >> To: [email protected] >> Sent: Friday, February 23, 2007 2:24 PM >> Subject: Re: [Repeater-Builder] Re: 220 repeater receiver > recommendations? >> >> >> >> For Scott: >> >> With respect to using the GE MII mobile frame for repeater > applications: >> >> 1. Can you say categorically that there is sufficient TX/RX > shielding to prevent any desense at any power level the conversion is > capable of operating? >> >> 2. When these converted mobiles operate with reduced TX power, > what happens to the output impedance of the TX? Is it still 50 ohms? > If not, does this affect the physical length of the half wave > interconnect cables often suggested between the TX and an isolator > and/or the cavities? >> >> 3. If the output of the TX is other than 50 ohms as a result of a > power level change, does it upset the adjustment of the downstream > isolator that has been tuned by a tracking generator? >> >> Tks >> >> Bruce >> K7IJ >> >> >> >> >> In a message dated 2/22/2007 7:02:38 P.M. Pacific Standard Time, > [EMAIL PROTECTED] writes: >> Ken, >> >> We not only do complete repeaters, we can custom build just > about anything you want or need. We can simply build a rock-solid > high-quality 220 receiver for you. We have done several receivers in > the past that are rack mountable in a 2 unit rack space. I have a GE > mastr II receiver that I am just finishing up. It came out looking so > nice that I am going to take pictures as a show piece. Micor receivers > would be VERY similar in construction. >> >> In my opinion, 2 things: >> >> 1. A Micor makes a much better repeater on 2M and 220 than a GE > MII. (sorry GE loyalists!!) I think a Mastr II makes a much better > repeater on UHF (sorry Micor loyalists!!) I would suggest a Micor for > your 220 Machine. >> >> 2. If you're going to spend money on a new receiver, why not > spend a bit more and get a completely new machine. Think about it, if > your receiver is not 100%, what's saying that your transmitter is > running at 100%? The notable thing about spectrum repeaters is that > they lived up to their name, they took up the WHOLE spectrum. This > might even be what is happing that you assume is a bad receiver. > Instead of a bad receiver, you may have a spurious transmitter that is > totally wiping your receiver off the map. Duplexers are meant to > isolate, but there is only so much they can isolate. >> >> If you'd like a quote on a new machine or a quote for a new > receiver, feel free to e-mail or call. >> >> Scott - Owner Repeater-Builder (the company) >> www.repeater-builder.com/custombuilt/ >> >> Scott Zimmerman >> Amateur Radio Call N3XCC >> 474 Barnett Road >> Boswell, PA 15531 >> ----- Original Message ----- >> From: Ken Harrison >> To: [email protected] >> Sent: Thursday, February 22, 2007 8:39 PM >> Subject: [Repeater-Builder] Re: 220 repeater receiver > recommendations? >> >> >> Thanks for the recommendation, Don. Though I'm sure a MastrII > would >> be a great conversion for 220, we (in the group sense) want to > try to >> save some of our money to get a remote base setup going on our >> repeater, too. Our small savings would be wiped out to replace the >> entire repeater, in spite of it being handy to have a complete > spare >> should there be a problem in the future. >> >> Thanks, >> Ken >> >> --- In [email protected], "Don KA9QJG" > <KA9QJG@> wrote: >> > >> > Ken first of All I noticed You stated Our group, so I would > assume >> You have >> > others kicking in to the Cost, I do not and I had Scott > build Me up >> a 220 >> > Repeater System, He did it in the process of Building a > house and >> Moving All >> > I had to do was Program the Controller, Hook up the Amp, > Power Supply >> > Duplexers, and Ant, I have never had any Problems for over a Yr. >> >> >> >> >> >> >> >> >> > ------------------------------------------------------------------------------ >> AOL now offers free email to everyone. Find out more about what's > free from AOL at AOL.com. >> >> >> >> >> > ------------------------------------------------------------------------------ >> >> >> No virus found in this incoming message. >> Checked by AVG Free Edition. >> Version: 7.5.441 / Virus Database: 268.18.3/699 - Release Date: > 2/23/2007 1:26 PM >> > > > > > > > > Yahoo! Groups - Join or create groups, clubs, forums & communities. > Links > > > > > > > -- > No virus found in this incoming message. > Checked by AVG Free Edition. > Version: 7.5.446 / Virus Database: 268.18.3/699 - Release Date: 2/23/2007 > 1:26 PM > >
