[Repeater-Builder] Need recommendation for small repeater controller
I'm once again looking for a small controller that fits within the multi-freq. area of a G.E. MVP radio. The available area is 5 x 2 x 1.25. The NHRC-micro is not a consideration, as it is the defective controller that is being replaced. Thanks. Bob NO6B
[Repeater-Builder] Unknown VHF Repeater
Hi, I uploaded some pics of my vhf repeater. I need a manual but I have no clue what the repeater is beyond the fact that it is a Motorola. Can anyone help? The pics are under the alblum named Unknown VHF Repeater. Thank you! Rod KB7WPU
[Repeater-Builder] Kenwood TKR-850 UHF Repeater with DB Products Full Size Duplexors For Sale
I have decided to sell my Kenwood TKR-850 UHF Repeater with DB Products Full Size Duplexors. It is on the air in Temple, TX on 444.500 123.0 tone. The package comes with programing cable and software. I am asking $1650 for the complete repeater syaytem. The repeater is type approved for commercial and GMRS if not used for amateur. Call Anthony at 254-493-8595.
[Repeater-Builder] Need help with Storno 9000 UHF Repeater
Hi all Need help with Storno 9000 UHF Repeater Need Manual and help to turn it in to a 70cm repeater Storno 9000 frequncy is on TX 423.20 RX 413.20 need to change the freguency to the ametuer band The Storno 9000 has its own radio in it and you can change it's frequency as listed below are the frquencys it currently transmits on. Hex Digit 1 = 423.196 3 = 423.796 5 = 423.996 7 = 424.396 9 = 424.796 B = 425.196 D = 425.596 F = 425.996 425.996 423.196 2.800 Mhz steps I have dumped the eprom and am not sure if it can be changed that way. Can any one help plz thank all
RE: [Repeater-Builder] Reducing power out when on battery backup.
Interestingly enough, for most repeaters with average use, the idle (receive) current over time is a more significant draw than the briefer periods of transmit. An additional modification that you can use to lower the idle current, is to remove power from the audio amp (of course, this will only work if you are feeding your repeater from the discriminator and don't want a local speaker). There is a single resistor that powers the audio amp, so you just lift that resistor. I don't have the R number handy, so consult the schematic. If you have problems figuring out which one, let me know and I'll look it up for you. IIRC, it is one of the resistors that live on the right side of the audio board (with the radio oriented with the big main connector and the RF ports towards you, and the PA away from you) between the discriminator enclosure and the wall of the radio. This will also allow you to eliminate the power resistor used to load the audio amp. I've done this on all of my MASTR II repeaters with no problems. Keith McQueen 801-224-9460 [EMAIL PROTECTED] -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Ed Yoho Sent: Tuesday, October 16, 2007 7:37 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Reducing power out when on battery backup. ldgelectronics wrote: Hello All, I have a requirement to install a battery backup system at a local ham repeater. It's a GE Mastr II running about 100 watts. With that much RF power, a couple of 100 AH batteries is only going to last a few hours. My first thought was to add a second lower power RF amp (something like 20 watts or so) and use coax switches tied to the AC mains to switch to the smaller amp when the AC power was out. This should give me a factor of 4 or 5 more amount of time on the backup batteries. The second thought (and here is where I need input), was to bring the variable resistor (R8 on the VHF version) from the 10 watt driver board to a smaller external board. Then add a second variable resistor and a relay to switch between the two. This should give me two independent amp settings that can be controlled by a single control. Is there any reason why this should not work? It would save the cost of the second smaller amp and two fairly expensive coaxial relays. The relay could be controlled from the repeater controller or automatically with just a 12v DC wall wart. Dwayne Kincaid WD8OYG Dwayne, A (hopefully) better method would be to use two RF relays to switch in or out the final stage of the stock amplifier. This will allow the sections to operate with their normal / nominal power settings and give a larger current reduction when in battery mode. relay 1 common to driver output relay 1 normally closed to final input relay 1 normally open to relay 2 normally open relay 2 normally closed to final output relay 2 common to antenna filter assembly This assumes the relays would be energized when in battery mode. A little more drain on the battery, but 99% of the time the coils would not need to be energized. Ed Yoho WA6RQD
Re: [Repeater-Builder] Unknown VHF Repeater
Looks like Motrac or Motran circuit boards but Micor channel elements and time-out timer. Mid 1960 to mid 1970 vintage. I've seen that round metering socket on Motracs. The SP11 won't make your job finding an exact manual any easier. Bob M. == --- rodandkathyjulian [EMAIL PROTECTED] wrote: Hi, I uploaded some pics of my vhf repeater. I need a manual but I have no clue what the repeater is beyond the fact that it is a Motorola. Can anyone help? The pics are under the alblum named Unknown VHF Repeater. Thank you! Rod KB7WPU Shape Yahoo! in your own image. Join our Network Research Panel today! http://surveylink.yahoo.com/gmrs/yahoo_panel_invite.asp?a=7
Re: [Repeater-Builder] Unknown VHF Repeater
Rod, The repeater is from the 60s and is part of the Motorola Motrak line. I did not see any tubes, but bet the finals are tube(s). I've seen a number of Motrak mobiles and base stations, but never one like this. The receiver looks like a common mobile unit so I am sure a mobile manual will give info. On second thought Mot did have a Motran line before the Micor line of the 70s 80s. This might be from this. I am sure there is a Mot veteran on here that can give more info. 73, ron, n9ee/r From: rodandkathyjulian [EMAIL PROTECTED] Date: 2007/10/16 Tue PM 06:10:57 CDT To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Unknown VHF Repeater Hi, I uploaded some pics of my vhf repeater. I need a manual but I have no clue what the repeater is beyond the fact that it is a Motorola. Can anyone help? The pics are under the alblum named Unknown VHF Repeater. Thank you! Rod KB7WPU Ron Wright, N9EE 727-376-6575 MICRO COMPUTER CONCEPTS Owner 146.64 repeater Tampa Bay, FL No tone, all are welcome.
[Repeater-Builder] Re: Unknown VHF Repeater
Thank you for all the input so far. I have the transmitter alighned but I am having trouble with the receiver. So, I'll try to find a mobile manual online. A brother ham brought over a desktop unit of the same era but it was too different. There are a few items stamped with 1970 on my repeater. Thanks again! Rod KB7WPU --- In Repeater-Builder@yahoogroups.com, Ron Wright [EMAIL PROTECTED] wrote: Rod, The repeater is from the 60s and is part of the Motorola Motrak line. I did not see any tubes, but bet the finals are tube(s). I've seen a number of Motrak mobiles and base stations, but never one like this. The receiver looks like a common mobile unit so I am sure a mobile manual will give info. On second thought Mot did have a Motran line before the Micor line of the 70s 80s. This might be from this. I am sure there is a Mot veteran on here that can give more info. 73, ron, n9ee/r From: rodandkathyjulian [EMAIL PROTECTED] Date: 2007/10/16 Tue PM 06:10:57 CDT To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Unknown VHF Repeater Hi, I uploaded some pics of my vhf repeater. I need a manual but I have no clue what the repeater is beyond the fact that it is a Motorola. Can anyone help? The pics are under the alblum named Unknown VHF Repeater. Thank you! Rod KB7WPU Ron Wright, N9EE 727-376-6575 MICRO COMPUTER CONCEPTS Owner 146.64 repeater Tampa Bay, FL No tone, all are welcome.
Re: [Repeater-Builder] Unknown VHF Repeater
Looks like a highband Motran repeater from about 1969 or so. All solid state, about 30 watts out. Something like C43MSY for a partial model number. What freq is it on now? Good RX, kinda of weird TX (by today's standard). Has three old style RF transistors in parallel to make the 30 watts out. This looks like it might have been a base station converted into a repeater. Joe --- rodandkathyjulian [EMAIL PROTECTED] wrote: Hi, I uploaded some pics of my vhf repeater. I need a manual but I have no clue what the repeater is beyond the fact that it is a Motorola. Can anyone help? The pics are under the alblum named Unknown VHF Repeater. Thank you! Rod KB7WPU __ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com
Re: [Repeater-Builder] Need recommendation for small repeater controller
Cut down your MP100 ;-) -Steve - Original Message - From: [EMAIL PROTECTED] To: Repeater-Builder@yahoogroups.com Sent: Tuesday, October 16, 2007 11:34 PM Subject: [Repeater-Builder] Need recommendation for small repeater controller I'm once again looking for a small controller that fits within the multi-freq. area of a G.E. MVP radio. The available area is 5 x 2 x 1.25. The NHRC-micro is not a consideration, as it is the defective controller that is being replaced. Thanks. Bob NO6B Yahoo! Groups Links
Re: [Repeater-Builder] Need recommendation for small repeater controller
Bob, What problems are you having with the micro? I am about to install my first one for a customer. Am I making a mistake?? Scott Scott Zimmerman Amateur Radio Call N3XCC 612 Barnett Rd Boswell, PA 15531 - Original Message - From: Steve Smith To: Repeater-Builder@yahoogroups.com Sent: Wednesday, October 17, 2007 12:16 PM Subject: Re: [Repeater-Builder] Need recommendation for small repeater controller Cut down your MP100 ;-) -Steve - Original Message - From: [EMAIL PROTECTED] To: Repeater-Builder@yahoogroups.com Sent: Tuesday, October 16, 2007 11:34 PM Subject: [Repeater-Builder] Need recommendation for small repeater controller I'm once again looking for a small controller that fits within the multi-freq. area of a G.E. MVP radio. The available area is 5 x 2 x 1.25. The NHRC-micro is not a consideration, as it is the defective controller that is being replaced. Thanks. Bob NO6B Yahoo! Groups Links -- No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.5.488 / Virus Database: 269.14.13/1075 - Release Date: 10/17/2007 9:38 AM
[Repeater-Builder] MASTR II
How can I tell if my MASTR II has a preamp built in? If it doesn't what is the best preamp to use? Thanks, Vern KI4ONW
RE: [Repeater-Builder] MASTR II
Sensitivity? HI Vern, Look in the front end helical / casting area where the receive coax connects to an RCA jack. There is a void area where the GE preamp goes. If you see the coax going to a small 1 ½ inch square-ish board with a tuning slug and see a short coax then going to the front end helicals, you have a preamp. Look at the pictures in the LBI for your radio and it will make sense. Don W5DK From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] Sent: Wednesday, October 17, 2007 12:02 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] MASTR II How can I tell if my MASTR II has a preamp built in? If it doesn't what is the best preamp to use? Thanks, Vern KI4ONW
[Repeater-Builder] New file uploaded to Repeater-Builder
Hello, This email message is a notification to let you know that a file has been uploaded to the Files area of the Repeater-Builder group. File: /FluX Research/TCX-12-D/TCX-12-D.GIF Uploaded by : dcflux [EMAIL PROTECTED] Description : Open Source: TinyCon2 Schematic. V1.1 10-17-2007 You can access this file at the URL: http://groups.yahoo.com/group/Repeater-Builder/files/FluX%20Research/TCX-12-D/TCX-12-D.GIF To learn more about file sharing for your group, please visit: http://help.yahoo.com/help/us/groups/files Regards, dcflux [EMAIL PROTECTED]
[Repeater-Builder] OT: Air Band Receiver
Off topic but I know there are some aviation techs on this list. I'm looking for a manual, or at a minimum the alignment instructions, for a General Electric air band VHF AM receiver Model # 4ERC-70-A3. I have one I want to change frequencies on and need the crystal calculation formula and the tune-up instructions. It looks a lot like one of the old GE ER-41-C VHF FM receivers from the Mastr Pro days. Thanks for any help and info. Doug VE7DRF
[Repeater-Builder] Re: New FCC Ruling May Benefit Many Ham Repeaters Located At Cell Sites
I passed this on to a friend and he doesn't believe it. Could you tell me where you read about it? Thanks! (he's in the backup power supply business so he got excited!) 73's Skip WB6YMH --- In Repeater-Builder@yahoogroups.com, Tony L. [EMAIL PROTECTED] wrote: If your repeater is located at a cell site, check this out: October 16, 2007 - A Federal Communications Commission representative said today that to meet national concerns for adequate public safety communications, it had adopted an order reinforcing and clarifying a prior order requiring cell phone and landline carriers within one year to install power backup supplies at all of their sites and to have portable power supplies available for sites that are incapable of having power backup. The ruling will clearly benefit the economic growth of generator, battery and fuel cell suppliers as well as installation contractors throughout the country. Public safety will be the prime beneficiary, but carriers and other telecom companies will be burdened with considerable expenses that will be incurred in order to meet the FCC's deadline -- impacting Adelstein's wished for success. The Commission's safety edict will result in increased administrative costs to tower owners to manage the new power supply installations that will ensure eight hours of power backup, but they will benefit from increased lease rates as their tenants expand their compound footprint.
Re: [Repeater-Builder] Reducing power out when on battery backup.
On Oct 16, 2007, at 10:10 PM, ldgelectronics wrote: It looks like the seperate small amp will be the best solution in terms of maximum battery life. I checked another repeater on the bench tonight and found pretty much the same thing as Ron mentioned. You can lower the RF power, but the efficency gets worse. After having read along the entire thread, I think you're probably right -- another PA that's more efficient at the lower power setting will work best for you, at least to get the project going. The trick is finding PA's with 250mW inputs, which is pretty low for most HT type PA's, etc. (It's not shown on their website, but Henry will modify their PA's for a 250mW input, according to a recent e-mail exchange I had with them about a Henry that the club owns but hasn't been useful to us, since we went to the MASTR II Station/Repeaters.) Anyway, to add more ideas -- I just thought I'd mention that there is a lower-power VHF stock MASTR II PA that only has the driver board, minus the final board, that has a coax jumper across to the low-pass filter board. Once in a while you see them on eBay. I believe it's 40W continuous-duty, but I'd have to go check the LBI's. There are also the mobile sticking out the back style of station PA's that are just the back end of a mobile sticking through a mounting plate that fits where the stock GE PA goes. They're not officially rated for continuous-duty, but could be turned down to a fairly low power if they had the same modification to remove the final board, and/or some came that way. (Again, I'd have to go pull up the LBI's for those to see how many different varieties GE made.) Any of those other stock lower-power GE PA's could be switched in and out by switching the exciter's output between the two PA's using a RF- rated relay, etc. Just another thing to think about... if you can find them. I have only run across one of the low-power VHF continuous-duty PA's, and it came from a remote-base setup for the railroad in Canada, apparently -- judging by the fact that it has a GE Canada badge, and I bought it from a Canadian. (GRIN) It only had two or three sets of heatsink fins, versus the usual full compliment across the back of the PA. It'd be easy to spot in photos in an eBay auction, etc. Might be something to keep an eye out for. -- Nate Duehr, WY0X
Re: [Repeater-Builder] MASTR II
On Oct 17, 2007, at 12:01 PM, [EMAIL PROTECTED] wrote: How can I tell if my MASTR II has a preamp built in? If it doesn't what is the best preamp to use? The other answer for how to see if it's in there, is correct. Kinda hard to explain if you haven't seen a normal one first... but there's an extra little board in the hole and a tiny RCA jumper from that board to the receiver. As far as the best preamp to use, that's very dependent on outside factors -- is your site quiet? Noisy? How much filtering are you doing? How much gain are you looking for? Example - at one local site, we run without a pre-amp because the noise floor from hundreds of transmitters and multiple broadcast stations there, is so bad -- that amplification just brings up more of the crud. We've talked about getting aggressive with the filtering and adding a light amount of pre-amp at that site, but it's not a priority for us right now. At another similarly noisy site, on VHF the hams use a shared antenna for receive, and the noise is so high there that the community pre- amp has been removed forever, because it caused nothing but problems -- and we're all doing filtering and our own pre-amplification AFTER our filters and duplexers, because the repeaters are literally spread across the band, and band-pass filtering and pre-amplification of the community feed is ineffective... it ends up being too wide. One repeater is at the bottom of 145 with a 144 input, and the others are at the top of 146, with mid 146 inputs. It's better to target a specific usable receiver sensitivity number that you'd like to see (after knowing what the site noise-floor looks like) than trying to work backward into the design from the pre-amp, but with that said... pre-amps that have been successfully used by many people here include: - The stock GE pre-amp (not much gain, but also not too unhappy in high noise environments) - Advanced Receiver Research (my favorite, but can be a little too hot for the MASTR II receivers we use) - Hamtronics (I don't like them, but others report good luck and behavior from them, and they're cheaper than most) - Angle Linear (Chip's got some nice stuff there, and it won't be cheap, but he'll also custom build some pretty nice setups if you work with him and answer his questions about your setup and site. I keep meaning to try out one of his PHEMPT pre-amps on one of our systems to see if we find any reason to use them over the GaAsFET ARR's... but haven't had any time to do it yet.) Just popping a pre-amp in without measuring useable sensitivity first, sometimes works out... but it's far better to measure and know how much it helped. If you measure, you can then tell if you've over-done it in the pre- amp (common when using the ARR... it's pretty hot) and perhaps you may want to add a 3 or 6 dB pad behind it to keep from overloading the receiver if it's dragging in a lot of extra stuff. You can measure the behavior of your specific receiver as you lower the signal (a set of different pads of different values or one of those accurate DF'ing switchable attenuators is nice during the testing). Remember, if you don't bandpass filter before a pre-amp, it's going to stuff a lot of off-channel extra signals (and noise) from other nearby transmitters -- or even far away ones! -- into your receiver. That off-frequency stuff, if strong enough is just going to make your receiver overload and may actually perform WORSE than without the pre- amplification. Another common problem is when people add pre-amplification and don't have enough isolation in the duplexer... now your transmitter is being heard by the receiver where it couldn't hear it previously... creating desense or just general deafness. It's all about trade-offs when you start going for the theoretical receiver limits. Sensitivity versus selectivity, the same ol' game whether you're talking about repeaters or any other weak-signal station's receiver. Maybe some of the pros here can share some of their pre-amplifier secrets. -- Nate Duehr, WY0X
[Repeater-Builder] theplanet.com is doing something odd with list messages from one of these YahooGroups lists
Just a head's up to the lists... [Re: Colorado Spectrum Report - Digital Repeaters] Regarding the message I sent with the subject line above, the message about the Spectrum Report has come back to me multiple times now as duplicates of my original message, and originally (without looking at the headers) I thought it was YahooGroups doing the duplication, (because they've done that before) but in this case, it's not... Actually I know for sure that today's example came from the posting to [dstar_digital], but I've gotten similar back from the RB and/or Illinois lists also, I think. (I was just deleting them, now I wish I'd kept all of them.) Some application (probably a mail to news gateway or similar) over at theplanet.com has a lovely internal mail loop going that apparently bounces some YahooGroups postings around in a circle between their own server (74.54.35.229) and itself as soon as the message is received from YahooGroups, which runs in circles to itself (so much for the mail admin knowing how to stop mail loops, they can't even stop them in their own server!), and then it eventually dumps it back to the sender originally listed on the message -- via their server at 74.54.35.237 8 days later. It has nothing to do with YahooGroups at all, I guess, but it is rather annoying. Can't really tell from here exactly what they're doing, but they're doing it wrong. If you're also getting the odd resent message that seems to have the same content as one you already received back from YahooGroups previously (especially if it's a message you sent and your own copy comes back to you)... apparently the owners of these servers mentioned above are doing it, and have something quite badly misconfigured. You can easily follow it in the headers/raw source of the messages, I just hadn't looked at them yet until today. (The third copy of this one, I finally decided I was annoyed and wanted to see what was doing it.) Nate WY0X On Oct 9, 2007, at 5:26 PM, Nate Duehr wrote: Received: from ed.23.364a.static.theplanet.com ([74.54.35.237] helo=out.wm001.com) by durango.natetech.com with esmtp (Exim 4.63) (envelope-from [EMAIL PROTECTED]) id 1IiEkh-0007zg-Sd for [EMAIL PROTECTED]; Wed, 17 Oct 2007 13:40:29 -0600 Received: from webmail.wm001.com [74.54.35.229] by out.wm001.com with ESMTP (SMTPD32-8.05) id A518F900120; Wed, 17 Oct 2007 19:40:08 + Received: from webmail.wm001.com [74.54.35.229] by webmail.wm001.com with ESMTP (SMTPD32-8.05) id AE017547009C; Tue, 09 Oct 2007 23:25:53 + Received: from webmail.wm001.com [74.54.35.229] by webmail.wm001.com with ESMTP (SMTPD32-8.05) id AE017546009C; Tue, 09 Oct 2007 23:25:53 + Received: from webmail.wm001.com [74.54.35.229] by webmail.wm001.com with ESMTP (SMTPD32-8.05) id AE017545009C; Tue, 09 Oct 2007 23:25:53 + Received: from webmail.wm001.com [74.54.35.229] by webmail.wm001.com with ESMTP (SMTPD32-8.05) id AE017544009C; Tue, 09 Oct 2007 23:25:53 + Received: from webmail.wm001.com [74.54.35.229] by webmail.wm001.com with ESMTP (SMTPD32-8.05) id AE017543009C; Tue, 09 Oct 2007 23:25:53 + Received: from n29a.bullet.scd.yahoo.com [66.94.237.31] by webmail.wm001.com (SMTPD32-8.05) id AE016D460102; Tue, 09 Oct 2007 23:25:53 + -- Nate Duehr [EMAIL PROTECTED]
RE: [Repeater-Builder] OT: Air Band Receiver
Doug, I have a complete GE microfiche file, but there is no listing for a 4ERC-70-A3 package. There are many listings that begin with 4ER but none with a C in the 4th place. Please confirm the model number. Perhaps you can find some numbers stamped on the edge of circuit boards. Any additional info will be very helpful in identifying your unit. 73, Eric Lemmon WB6FLY -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Davies, Doug A FOR:EX Sent: Wednesday, October 17, 2007 2:17 PM To: Repeater-Builder Subject: [Repeater-Builder] OT: Air Band Receiver Off topic but I know there are some aviation techs on this list. I'm looking for a manual, or at a minimum the alignment instructions, for a General Electric air band VHF AM receiver Model # 4ERC-70-A3. I have one I want to change frequencies on and need the crystal calculation formula and the tune-up instructions. It looks a lot like one of the old GE ER-41-C VHF FM receivers from the Mastr Pro days. Thanks for any help and info. Doug VE7DRF
Re: [Repeater-Builder] MASTR II
I do have a band pass filter in front of my receiver now. The site is pretty quiet as it's at my house and I don't have a lot of transmitters around. A couple of the guys that help me out were saying I should put a 5 to 7 db preamp on it. The real MASTR II one sounds like it might be a good one. Thanks, Vern On Wed, 17 Oct 2007 18:49:02 -0600 Nate Duehr [EMAIL PROTECTED] wrote: On Oct 17, 2007, at 12:01 PM, [EMAIL PROTECTED] wrote: How can I tell if my MASTR II has a preamp built in? If it doesn't what is the best preamp to use? The other answer for how to see if it's in there, is correct. Kinda hard to explain if you haven't seen a normal one first... but there's an extra little board in the hole and a tiny RCA jumper from that board to the receiver. As far as the best preamp to use, that's very dependent on outside factors -- is your site quiet? Noisy? How much filtering are you doing? How much gain are you looking for? Example - at one local site, we run without a pre-amp because the noise floor from hundreds of transmitters and multiple broadcast stations there, is so bad -- that amplification just brings up more of the crud. We've talked about getting aggressive with the filtering and adding a light amount of pre-amp at that site, but it's not a priority for us right now. At another similarly noisy site, on VHF the hams use a shared antenna for receive, and the noise is so high there that the community pre- amp has been removed forever, because it caused nothing but problems -- and we're all doing filtering and our own pre-amplification AFTER our filters and duplexers, because the repeaters are literally spread across the band, and band-pass filtering and pre-amplification of the community feed is ineffective... it ends up being too wide. One repeater is at the bottom of 145 with a 144 input, and the others are at the top of 146, with mid 146 inputs. It's better to target a specific usable receiver sensitivity number that you'd like to see (after knowing what the site noise-floor looks like) than trying to work backward into the design from the pre-amp, but with that said... pre-amps that have been successfully used by many people here include: - The stock GE pre-amp (not much gain, but also not too unhappy in high noise environments) - Advanced Receiver Research (my favorite, but can be a little too hot for the MASTR II receivers we use) - Hamtronics (I don't like them, but others report good luck and behavior from them, and they're cheaper than most) - Angle Linear (Chip's got some nice stuff there, and it won't be cheap, but he'll also custom build some pretty nice setups if you work with him and answer his questions about your setup and site. I keep meaning to try out one of his PHEMPT pre-amps on one of our systems to see if we find any reason to use them over the GaAsFET ARR's... but haven't had any time to do it yet.) Just popping a pre-amp in without measuring useable sensitivity first, sometimes works out... but it's far better to measure and know how much it helped. If you measure, you can then tell if you've over-done it in the pre- amp (common when using the ARR... it's pretty hot) and perhaps you may want to add a 3 or 6 dB pad behind it to keep from overloading the receiver if it's dragging in a lot of extra stuff. You can measure the behavior of your specific receiver as you lower the signal (a set of different pads of different values or one of those accurate DF'ing switchable attenuators is nice during the testing). Remember, if you don't bandpass filter before a pre-amp, it's going to stuff a lot of off-channel extra signals (and noise) from other nearby transmitters -- or even far away ones! -- into your receiver. That off-frequency stuff, if strong enough is just going to make your receiver overload and may actually perform WORSE than without the pre- amplification. Another common problem is when people add pre-amplification and don't have enough isolation in the duplexer... now your transmitter is being heard by the receiver where it couldn't hear it previously... creating desense or just general deafness. It's all about trade-offs when you start going for the theoretical receiver limits. Sensitivity versus selectivity, the same ol' game whether you're talking about repeaters or any other weak-signal station's receiver. Maybe some of the pros here can share some of their pre-amplifier secrets. -- Nate Duehr, WY0X
Re: [Repeater-Builder] MASTR II
At 10/17/2007 17:49, you wrote: It's better to target a specific usable receiver sensitivity number that you'd like to see (after knowing what the site noise-floor looks like) than trying to work backward into the design from the pre-amp, but with that said... pre-amps that have been successfully used by many people here include: My comments on the ones I've used: - The stock GE pre-amp (not much gain, but also not too unhappy in high noise environments) The P1dB point on the UHF UHS preamp I measured was only +1.5 dBm. However, it's much narrower than any standalone preamp you can buy off the shelf, so it has some inherent out-of-band rejection. I measured a noise figure of 4.6 dB, which sounds a bit high but it's a LOT lower than the noise figure of a stock UHF GE MVP/Mastr II/Exec II RX. I just installed a VHF UHS preamp in my latest 2 meter portapeater am very happy with its performance so far. - Advanced Receiver Research (my favorite, but can be a little too hot for the MASTR II receivers we use) No personal experience with this one, though some have questioned whether it's unconditionally stable (meaning it won't oscillate no matter how it's terminated on its input output). - Hamtronics (I don't like them, but others report good luck and behavior from them, and they're cheaper than most) I'm using their LNY series preamp on a UHF remote receiver. It was very cheap at the time (~$30), but I had to package the board myself. Hamtronics claimed a NF of 0.8 dB but no way could I get it down below 2.2 dB, even when tuning it directly on an HP noise figure meter. The P1dB was reasonable for a MOSFET preamp: +7 dBm. Looking at their current offerings, I'd shop around as their enclosure doesn't look to be RF tight. Those clam-shell cases tend to seal poorly around the seams, resulting in so much leakage you'd be better off leaving the top off. - Angle Linear (Chip's got some nice stuff there, and it won't be cheap, but he'll also custom build some pretty nice setups if you work with him and answer his questions about your setup and site. I keep meaning to try out one of his PHEMPT pre-amps on one of our systems to see if we find any reason to use them over the GaAsFET ARR's... but haven't had any time to do it yet.) Chip used to give hams a discount (25%?) from the prices shown on his web page. If he still does, they're actually quite reasonable. And of course you get the guarantee of unconditional stability. The packaging is beyond reproach, with hefty EMI feedthrus for power N connectors for RF I/O. I think he uses enclosures from Compac RF, which are about as good as you can get. Remember, if you don't bandpass filter before a pre-amp, it's going to stuff a lot of off-channel extra signals (and noise) from other nearby transmitters -- or even far away ones! -- into your receiver. That off-frequency stuff, if strong enough is just going to make your receiver overload and may actually perform WORSE than without the pre- amplification. Many preamps are VERY wideband. One of Chip's 440 MHz units actually measured lower NF at 800 MHz than at 440 MHz, was still quite usable @ 222 MHz. This is not to say anything is wrong with his preamps; they operate this way by design. It's up to the user to provide proper input filtering. Bob NO6B
[Repeater-Builder] Failed MastrII
Buddy of mine has lost the amplifier section of his MASTR II repeater. Need a base station transmitter or in worse case a Mobile transmitter complete. This is a high band unit presently on 147.2. Anybody have one laying around that is surplus to your needs? Gary - K7NEY
[Repeater-Builder] off topic
Does any one know of a way to get a kenwood tk-6110 lowband to accept a 6 meter freq? Thanks, Mike KA2NDW
