Recrystal MSR-2000 Channel Elements
> "Path_Finder.Geo" <kb1...@...> wrote: > Hi everyone, I am going to post this message here because > batlabs didn't approve my post. Apparently it's too harsh > to tell people, "PLEASE DO NOT TELL ME TO HAVE SOMEONE > ELSE DO IT." Hi Jeff, Apparently you do not play the BatLabs Game very well? I'm sure you'll survive with the ever so perky bunch over here. > I am looking for information on how exactly to re-tune > a channel element for a MSR repeater. I've seen > instructions as far as what to adjust on the element > itself, but what I really need to know is; what equipment > is required, how to hook that equipment up to the channel > element, and what to look for while adjusting the channel > element. The transmit channel element is best adjusted for frequency center by using a Communications Service Monitor setup to sample (off the on-air signal) read the main carrier channel/frequency. The simple way to set the IDC Control/Pot is to set the Transmit CTCSS (PL) Tone deviation to about 750Hz. In a stock MSR-2000 the repeat audio level is then set using the level pot on the Squelch Gate Module. If you don't have access to a Service Monitor, a decent Frequency Counter will at least let you "net" (adjust) the frequency to F-center (on the desired frequency). If you move the transmitter more than say... 500 kHz from its last alignment location, you should repeat the Service Manual Alignment steps on or near the new frequency. The Receiver is a different animal. Take the Receiver frequency and add and/or subtract the receiver IF frequency (most often 10.7 or 10.8 MHz for the VHF Receiver). The formula you use depends on your receivers IF Frequency and "Injection Chain", which translates to which side of the IF the multiplied crystal frequency ends up on. In your example it's probably F-frequency minus the IF Frequency equals the multiplied Channel Element injection frequency, which is what you want to set/align. Put a X1 Scope/Text Probe on your Service Monitor (or Frequency Counter) Antenna (Low Level RF) Input and place it down onto/near the receiver circuit board. You can also use a decent quality frequency counter if you're more careful. At some location on or near the board you will be able to monitor and measure the output of the RX Channel Element Frequency, then set it for the expected Injection Frequency. As an example: A receive frequency of 151.625 MHz minus a 10.7 IF frequency equals 140.925 MHz. "Sniff" around the receiver board until you observe a signal in that area, then "net" (adjust) the channel element frequency to the expected 140.925 F-center location. If you can't find the expected frequency you might run the numbers for a 10.8 IF Frequency and sniff around 140.825 for the channel element injection frequency. In both the above examples, a X1 (times-1) Scope Probe or something similar is handy to use. If you can't get/find a signal, make a short antenna probe by clipping a small length of insulated regular wire onto the end of the probe. The end of the wire held by the Scope Probe "jaws" should obviously be stripped bare. Try not to allow the sampling wire and/or probe to directly contact/short any of the exposed metal parts on the receiver board. > Now I realize that I need a new crystal as well, and I > realize it can all be done professionally with temperature > compensation. Yeah but in many cases "professional" is a lot more expensive than it really has to be. > But what I want to know is how I can do it myself just > to get started and make sure everything is going to work > the way I want before I pay out big bucks to have it all > done the right way. I have an extra set of channel > elements, so playing around with one set isn't going to > affect having the other set done professionally if I > mess something up. For me there are two regular places to order crystals. The first is International Crystal Manufacturing, always high quality but you will find the pricing a bit steep for any casual crystal/channel element work. The second location for me is Bomar, where I pretty much buy all my channel element crystals. Their quality, pricing and wait time is in my opinion more than fair. Their only down side (to me) is their $50 min order amount. So you might need to order a few extra crystals to make an order amount. Not a problem if you think ahead or pal-up with someone else to place an order. I call Bomar with a Visa Card in the other hand, tell them I want Crystals for Mitrek/MSR-2000 Channel Elements KXN-1086 and KXN-1088 types. There are other MSR Channel Element numbers you can use, but the above model numbers are the most popular and should be interchangeable with anything you might have. At a price of about $15/$20 per crystal (last time I had some cut) I order at least 4 crystals to make the min order amount. Wait the normal time (they do have rush service for more $$) and the "rocks" show up at your door. Carefully remove the Channel Element Cover along with the insulating sleeve and desolder the old crystal, replacing it with your new rock. Replace the cover, label the channel element with the new frequency and your ready to rock and roll. > Thanks for any help you can give me, > Jeff - KB1SPH / WQEX694 There are other places to buy crystals but I haven't used their services so I obviously have no qualified comments on those sources. Good luck Jeff... jump in, the water is fine (but it's deep) cheers, s. http://simplyrecipes.com/recipes/perfect_guacamole/
