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 >
