Re: [Repeater-Builder] Re: Hamtronics 6 meter repeater problems
Hello Ron, My 53.41Mhz repeater here in Connecticut has been on the air for years using a MASTRII conversion. I have had very few problems over the years with this equipment. The Hamtronics that I have belongs to a club and I was trying to help them get it up and operational. I think I will be bringing them some bad news. 73, Joe, k1ike Ron Wright wrote: Joe, Your decision would have been mine from the start. A GE Mastr II or Exec II make very good 6 meter repeaters and not for much money if you want to do some of the work. For 6 meters the comb number would end in a 33, 42-50 MHz, and will most often move up into 6 meters. On the board is the conversion. Good luck. 73, ron, n9ee/r .
Re: [Repeater-Builder] Re: Hamtronics 6 meter repeater problems
Joe, Would you be willing to send me the exciter for experimental modification? Kevin Custer I think I am coming to the realization that this transmitter strip might end up on the shelf too. I've been trying to fix this for a local club and I think I have finally given up. I hate to admit defeat, but it looks like it is not fixable without major circuit modifications. I'm going to start looking around my basement for some GE MASTRII lowband parts. i have a few UHF MASTRII repeater chassis around and all I need to do is change out the boards. Back to something that I am familiar with, MASTRII stuff. 73, Joe, K1ike
[Repeater-Builder] Re: Hamtronics 6 meter repeater problems
It is more than possible you have a crystal cut on the wrong mode. It's not hard to order replacement crystals although you run into the min order or higher costs depending on where the new rocks are ordered. You might order and try both the oven and non-oven operation. I run a TA51 6 Meter Exciter without the OV-1 oven, which on low band is not that big of a problem. Crystal controlled (non-synth) equipment is being pushed aside by current technology. If you want a practical alternative... buy a Midland XTR Low band Mobile off EBay, reprogram it onto the six meter band, retouch/adjust the vco, receiver front end tx sections for the higher range and you're off and running. I've got a few Syntech and XTR Mobiles already on six... and they make great repeaters. Not to mention there is a yahoo group for Midland Radios. cheers, skipp Joe [EMAIL PROTECTED] wrote: I'm thinking that I might just have a bad crystal, but have no way to prove it. The crystal does have the Hamtronics crystal oven on it, but I don't think that should be the problem. My opinion right now is that the TA51 6 meter version is just not a good design and probably should be pulled from the Hamtronics products. The specifications on the website state that the transmitter can do +-5Khz of deviation, but the instructions say that it cannot. The 6 meter repeater that they now sell uses a different synthesized transmitter. 73, Joe, K1ike Kevin Custer wrote: Joe wrote: The distortion is acceptable at 2.5Khz deviation, but not at 3Khz. I have had the 144Mhz and 220Mhz versions of this board and never had this problem. As you said earlier Joe, it's the multiplication factor that is killing you, with this type of phase modulator. I have never tried my FM modification on a 6M TA-51. I do however use it on UHF where the FM modulator replaces the phase modulator totally. I know I advertise that my FM mod is only for PL generation , but if driven from a good clipper/filter, like the AP-50, you can use it on the entire voice/pl range. It may be difficult to FM a crystal far enough to get 5K of totally undistorted audio from a Hamtronics 6M TA-51, but I'd try it. Use a good varactor. http://www.repeater-builder.com/hamtronics/ta-51pl_mod.html http://www.repeater-builder.com/products/ap-50.html Kevin
[Repeater-Builder] Re: Hamtronics 6 meter repeater problems
Well... The crystal could easily be the problem. Group member Sal sent me a Uniden ARU-251 Repeater to re-crystal and align. The crystal was cut on the wrong mode and a real cluster $#* to the problem sort out. The transmitter would partially align but not remain stable. The sanity check was the repeater arrived known operational (on the original frequency) and I had spare Uniden Repeater crystals in the shop. I was able to confirm the wrong mode xtal by using the trusty (and great dollar value as often found on Ebay) crystal check function built into a Sencor FC-71 frequency counter. [if you haven't got a great frequency counter... get a working Sencore FC-71 off Ebay. It's a sleeper deal of the day] I had Bomar cut new crystals in the right mode and after install and alignment the transmitter performed exactly as it should. I traced the wrong crystal mode/operation problem back to a typo which the original xtal order was placed. I/we just put it down to experience. s. Kevin Custer [EMAIL PROTECTED] wrote: I wouldn't think so, the crystal itself is not 'modulated'; it's the following active stage that provides the modulation. Kevin Joe wrote: I'm thinking that I might just have a bad crystal, but have no way to prove it. The crystal does have the Hamtronics crystal oven on it, but I don't think that should be the problem.
Re: [Repeater-Builder] Re: Hamtronics 6 meter repeater problems
skipp025 wrote: Well... The crystal could easily be the problem. How? I don't think he was having any trouble tuning it up, getting expected power output, or having stability issues; he is only complaining about proper modulation capability. Kevin
Re: [Repeater-Builder] Re: Hamtronics 6 meter repeater problems
Sorry, but it does not belong to me or I would. This belongs to the local club that I am helping out. 73, Joe, K1ike Kevin Custer wrote: Joe, Would you be willing to send me the exciter for experimental modification? .
Re: [Repeater-Builder] Re: Hamtronics 6 meter repeater problems
Joe wrote: Sorry, but it does not belong to me or I would. This belongs to the local club that I am helping out. When you talk to them Joe, see if they would be willing to send the exciter to me. I'd be willing to do some experimenting on it to see if it could be FM'd satisfactorily. I don't think the experimentation would ruin the unit or other compromise it. If they aren't going to use it anyway, maybe they would be willing to allow me to try it. I'll offer to do the experiment for free, and return it whether the operation is a success, or not. Kevin Custer Repeater Builder
Re: [Repeater-Builder] Re: Hamtronics 6 meter repeater problems
I'm thinking that I might just have a bad crystal, but have no way to prove it. The crystal does have the Hamtronics crystal oven on it, but I don't think that should be the problem. My opinion right now is that the TA51 6 meter version is just not a good design and probably should be pulled from the Hamtronics products. The specifications on the website state that the transmitter can do +-5Khz of deviation, but the instructions say that it cannot. The 6 meter repeater that they now sell uses a different synthesized transmitter. 73, Joe, K1ike Kevin Custer wrote: Joe wrote: The distortion is acceptable at 2.5Khz deviation, but not at 3Khz. I have had the 144Mhz and 220Mhz versions of this board and never had this problem. As you said earlier Joe, it's the multiplication factor that is killing you, with this type of phase modulator. I have never tried my FM modification on a 6M TA-51. I do however use it on UHF where the FM modulator replaces the phase modulator totally. I know I advertise that my FM mod is only for PL generation , but if driven from a good clipper/filter, like the AP-50, you can use it on the entire voice/pl range. It may be difficult to FM a crystal far enough to get 5K of totally undistorted audio from a Hamtronics 6M TA-51, but I'd try it. Use a good varactor. http://www.repeater-builder.com/hamtronics/ta-51pl_mod.html http://www.repeater-builder.com/products/ap-50.html Kevin
Re: [Repeater-Builder] Re: Hamtronics 6 meter repeater problems
Good choice. I almost suggested it. Or an MVP/Exec II. Chuck WB2EDV - Original Message - From: Joe [EMAIL PROTECTED] To: Repeater-Builder@yahoogroups.com Sent: Wednesday, November 21, 2007 8:56 PM Subject: Re: [Repeater-Builder] Re: Hamtronics 6 meter repeater problems I think I am coming to the realization that this transmitter strip might end up on the shelf too. I've been trying to fix this for a local club and I think I have finally given up. I hate to admit defeat, but it looks like it is not fixable without major circuit modifications. I'm going to start looking around my basement for some GE MASTRII lowband parts. i have a few UHF MASTRII repeater chassis around and all I need to do is change out the boards. Back to something that I am familiar with, MASTRII stuff. 73, Joe, K1ike Chuck Kelsey wrote: Years ago I built a Hamtronics 6-meter exciter. Suffered from low and distorted audio too. And it was a bear to keep it tuned up. Tuning caps were real touchy. I never did actually use it. It sits in a box in the basement. One of those lessons learned projects. Chuck WB2EDV Yahoo! Groups Links
Re: [Repeater-Builder] Re: Hamtronics 6 meter repeater problems
I think I am coming to the realization that this transmitter strip might end up on the shelf too. I've been trying to fix this for a local club and I think I have finally given up. I hate to admit defeat, but it looks like it is not fixable without major circuit modifications. I'm going to start looking around my basement for some GE MASTRII lowband parts. i have a few UHF MASTRII repeater chassis around and all I need to do is change out the boards. Back to something that I am familiar with, MASTRII stuff. 73, Joe, K1ike Chuck Kelsey wrote: Years ago I built a Hamtronics 6-meter exciter. Suffered from low and distorted audio too. And it was a bear to keep it tuned up. Tuning caps were real touchy. I never did actually use it. It sits in a box in the basement. One of those lessons learned projects. Chuck WB2EDV
Re: Re: [Repeater-Builder] Re: Hamtronics 6 meter repeater problems
Joe, Your decision would have been mine from the start. A GE Mastr II or Exec II make very good 6 meter repeaters and not for much money if you want to do some of the work. For 6 meters the comb number would end in a 33, 42-50 MHz, and will most often move up into 6 meters. On the board is the conversion. Good luck. 73, ron, n9ee/r From: Joe [EMAIL PROTECTED] Date: 2007/11/21 Wed PM 07:56:31 CST To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Re: Hamtronics 6 meter repeater problems I think I am coming to the realization that this transmitter strip might end up on the shelf too. I've been trying to fix this for a local club and I think I have finally given up. I hate to admit defeat, but it looks like it is not fixable without major circuit modifications. I'm going to start looking around my basement for some GE MASTRII lowband parts. i have a few UHF MASTRII repeater chassis around and all I need to do is change out the boards. Back to something that I am familiar with, MASTRII stuff. 73, Joe, K1ike Chuck Kelsey wrote: Years ago I built a Hamtronics 6-meter exciter. Suffered from low and distorted audio too. And it was a bear to keep it tuned up. Tuning caps were real touchy. I never did actually use it. It sits in a box in the basement. One of those lessons learned projects. Chuck WB2EDV Ron Wright, N9EE 727-376-6575 MICRO COMPUTER CONCEPTS Owner 146.64 repeater Tampa Bay, FL No tone, all are welcome.
Re: [Repeater-Builder] Re: Hamtronics 6 meter repeater problems
Joe, I bought 4 GE Mastr II 48 mHz exciters off Ebay back during the summer for $1.25 each and they all tuned up on the only xtal I had in the six meter band - 53.4 mHz. They can be a bear to tune, so just be patient if you come up with one of them to move into the band. It took me quite a while to get the first one tuned, but then I pre-positioned the slugs in the other three based on the first one and just touched them up with power on them. All produced 250+ mW with no mods, and all modulated 5 kHz with a 1 kHz tone and low distortion. Good luck - 73 - Jim W5ZIT --- Joe [EMAIL PROTECTED] wrote: I think I am coming to the realization that this transmitter strip might end up on the shelf too. I've been trying to fix this for a local club and I think I have finally given up. I hate to admit defeat, but it looks like it is not fixable without major circuit modifications. I'm going to start looking around my basement for some GE MASTRII lowband parts. i have a few UHF MASTRII repeater chassis around and all I need to do is change out the boards. Back to something that I am familiar with, MASTRII stuff. 73, Joe, K1ike Chuck Kelsey wrote: Years ago I built a Hamtronics 6-meter exciter. Suffered from low and distorted audio too. And it was a bear to keep it tuned up. Tuning caps were real touchy. I never did actually use it. It sits in a box in the basement. One of those lessons learned projects. Chuck WB2EDV Get easy, one-click access to your favorites. Make Yahoo! your homepage. http://www.yahoo.com/r/hs
[Repeater-Builder] Re: Hamtronics 6 meter repeater problems
Joe [EMAIL PROTECTED] wrote: Hello to All, I am presently working on a Hamtronics 6 meter repeater and am finding it quite disappointing. Sorry to read the above comment ... I've always had good luck and a lot of great learning experiences with Hamtronics gear. Dealing with Jerry at Hamtronics is sometimes a pain but other times he can be a very nice guy. This repeater is owned by a local club and has had problems from the beginning. The Club or the Repeater? :-) R100 receiver. I have this working quite well, except for the fact that it only gives 100mv of audio to the controller. The NHRC controller I am using likes to see 1 volt of audio. I guess I might have to add a stage of amplification. There are three or four ways to deal with the receiver audio from Hamtronics and similar Receiver Boards. Hamtronics uses two options and both work very well for what they are. The first is to tap the volume control pot on the high side for constant audio. You get what you get in level but most often deal with the level in later stages. Another method is to terminate the speaker audio output into a 22 or 27 ohm resistive load. You AC Couple the terminated audio to the next stage and simply use the volume pot as your level control. Consider the output from the above methods might contain ctcss information (any transmitted sub-audible tones) so running the repeater audio through a filter like the on-board Comm-Spec TS-32 board is a great idea. Then you simply inject the ctcss tone output from the TS-32 board direct to the transmitter for strip (remove) and regenerate ctcss operation. In cases of low recovered audio you can sometimes modify a Repeater Controller input op-amp stage for additional gain. All this depends on the specific controller design. A few controller mfgrs actually have input stage dip and basic pc-board jumper mods to set the controllers audio pot input range value. And the choice of adding a small amplifier circuit remains an option. You can do a simple circuit board or buy complete op-amp circuits in kit form from Jameco, Vellemum, Rainbowkits and many other locations. Check out Jameco's online catalog for more kit information. You could also use the famous LM-386 audio amplifier kit terminated as described above. Chips like the 5532 op amp make great audio buffer and line driver circuits. TA51 transmitter. Here is the real problem. I can only get 2.5Khz deviation of clean 1000Hz audio out of the transmitter. I can push it to 3Khz, but it gets distorted. Using the same TA-51 tx board... I don't have that problem. You must use a low impedance, high power audio source to drive the audio input. Many repeater controller audio output stages simply don't have enough drive for a low band transmitter. I would suspect the NRHC Controller audio output circuit doesn't have enough drive for the transmitter. It's a pretty common problem... Looking at the manual for the TA51 6 meter version, I see a note that states the following: Because the fundamental frequency is only multiplied by 6 (instead of 12 for 144 MHz), the frequency deviation is only 1/2 of what it would be on high-band. Hence the reason many low band transmitters need much more audio drive energy. Therefore, it may not be possible to obtain a full ±5 kHz deviation with modulation without a little distortion. This should not be objectionable though. The distortion Hamtronics is talking about is probably not what you are or have experienced. The distortion I actually hear from my TA-51 exciter board is not very much at all. In many cases only a trained ear might object to the typical phase modulator distortion. This seems totally unacceptable to me and it looks like it is not fixable. Trying to Phase Modulate the transmitter with more than 2.5Khz deviation causes it to distort and shift frequency. Most anything is fixable... just a question of how much time you want to spend working on it. Also, the audio stages distort at the levels that hamtronics specifies at the test points. Only the first amplifier stage seems to run clean. Any comments? (except for Don't buy Hamtronics!) I find this disappointing because I have had other Hamtronics that performed well, or very well, for the money. 73, Joe, K1ike Sure... try driving the transmitter audio input from an honest low impedance source - line driver circuit. I'm using an old GE Master-Pro Line Driver circuit board (found in tone remotes and repeaters) with great results. cheers, s.
