Excellently written Kevin. I really enjoy your writings. I think that you should have been an author if the radio tech didn't work out. I value your opinion. Very well put..
Until Next Time Steve Johnson --- In [email protected], Kevin Custer <[EMAIL PROTECTED]> wrote: > Don Pomplun wrote: > > >Our local volunteer excursion railroad is growing to the point where > >simplex radio communications is not filling the need (adding another 3 > >miles of track, windy railroad, multiple trains). So "going repeater" is > >an option. I have seen articles & ads about converting a GE Master Exec II > >series radio for repeater operation. > > > >Yesterday I was scrounging around our stash and found a single GE > >radio. Maybe you can tell me what I've got and its potential. Name plate > >data is: > >GE Mastr II > >comb MX56KAS66A > >ser 8493743SPL > >FCC TX Data KT-32-B > >FCC RX Data ER-64-A > > > > It would make a fine repeater. Instructions for doing so are located here: > http://www.mastr2.com/ > > >We also have a number of Motorola Micor series radios, and I'd welcome comments on their suitability vs the GE. > > > > I'll break a Cardinal Rule here, but since I am doing it technically > speaking, here goes: > First off, I'll tell you that I enjoy converting both the GE Mastr II > and the Motorola Micor Mobile radio sets to repeaters. Both work very > well, and have NO internal desense issues when converted properly. In > all cases the GE Mastr II is an easier conversion, but easier doesn't > necessarily mean it's better. That being said, I do have favorites. On > High-band, 2 Meters and 220, the Micor is my choice, mainly due to two > things; the receiver and the squelch circuitry. For 2M and 220, we can > build a better working receiver from the Micor, and the transmitter > works as well as the Mastr II. On UHF, the Mastr II is my choice, > mainly due to it being conventional in nature. The Micor UHF mobile is > a weird radio; it doesn't have a conventional exciter (Ref 1) <#Ref_1>. > It's transmitter frequency is derived from receiver circuitry, and the > Power Amplifier is very inefficient and can be troublesome. Getting > back to VHF, the Micor is a more difficult radio to convert to a > repeater. It's more difficult to convert the RF circuitry, and it is > more difficult to convert to duplex, however ICS Controllers > <http://www.ics-ctrl.com/controllers.html> is making a new controller > (the SingleM) to make it easier to do the Micor Mobile to repeater > conversion. This controller comes in response to the NHRC/M2 > controllers <http://www.nhrc.net/ge-stuff.php> that make Mastr II mobile > repeater conversion painless. > > While the GE Mastr II has a very wide tuning range, its stability of > tuning is compromised as compared to the Micor. The Micor was built in > several 'ranges' in which the radios were designed to be operated. When > operated within these ranges, the radio will meet or exceed factory > specifications; however when operated outside these ranges, the > performance of the radio falls off quite rapidly (Ref 2). <#Ref_2> On > the contrary, the Mastr II will operate quite well outside of its > factory stated ranges. The reason this happens is in the way the radio > sets are designed. The GE Mastr II utilizes tuning capacitors or > trimmer capacitors to tune many of the stages, especially in the > receiver. The Micor uses tuned inductors (coils) to tune most of the > stages, in either the receiver or exciter. By nature, a wider tuning > range is available by using a tuning capacitor, but, at the result of > the stage being touchier to tune right on the money, and the ability of > it staying in tune. This allows a 150.8 to 174 MHz. Mastr II to be used > in the 2 meter band or a 450 to 470 MHz unit to be used in the 440 ham > band with little or no 'conversion' of the RF circuitry, but again, at > the cost of some instability. The Micors' tuning is limited by the > mechanical range of the tuning slug. This allows a smoother more > precise adjustment of each stage, but, the Micor *must* be either > originally built or 'properly converted' to operate on the frequency in > which it is to be used. This required conversion makes it more > difficult for us to build a repeater from available surplus commercial > radios for the different ham bands, but I feel a better product results. > > I worked in the local Motorola Service Shop (MSS) in the late 70's and > early 80's when the Micor and Mastr II were head to head competition. I > had the opportunity to service both the Micor and Mastr II during this > time; as the local shop was obligated to service whatever was on the > service contract. This is where most of my expertise and opinion on > these two comes from. We had a saying: "One thing you never have to do > is re-tune a Micor, even if it is riding inside a Dragline. One thing > you always have to do is re-tune those [EMAIL PROTECTED] Mastr II's, even if > it is > riding in the back seat of a Cadillac..." > > I have literally spent days working on the modifications for both the GE > Mastr II and Motorola Micor for proper 2 meter and 220 operation. It > seems I can always make a Micor out perform the Mastr II where receiver > sensitivity is concerned (Ref 3). <#Ref_3> Although to be quite fair in > this statement, I rarely have the opportunity to use a real 2 meter > Mastr II, but may statement stands on the 220 band. In my opinion, the > receiver is the most important part of the repeater, and a properly > working one is a must for the repeater to operate correctly. The > carrier squelch is another item that must work correctly in a good > operating repeater. In my opinion, nothing beats the squelch operation > of the famous Micor Squelch Chip (Ref 4). <#Ref_4> In fact, the Micor > Squelch works so well, companies have built boards to install in non > Micor radios to give them the same Micor type squelch operation. The > Link Comm RLC-MOT is such a board that we offer as an option to be > installed into our GE conversions (Ref 5). <#Ref_5> As I stated > earlier, the UHF is another story, the GE Mastr II mobile conversion is > better, hands down, than a Micor UHF mobile conversion, although the > Micor UHF Station is simply hard to beat. > > These are the basic differences between the two radio sets, and why I > prefer one over the other. While there are other more technical issues > that can determine which radio set I prefer, I won't get into them > unless you want the whole $2.00 tour. Here are some references in the > form of web pages that go into more detail on the things I spoke of in > the text above: > > (Ref 1) http://www.repeater-builder.com/rbtip/micoruhfmobile.html > (Ref 2) http://www.repeater-builder.com/rbtip/micorvhfboardnumbers.html > (Ref 3) http://www.repeater-builder.com/rbtip/222sensitronRX.html > (Ref 4) http://www.repeater-builder.com/rbtip/micorsquelch.html > (Ref 5) http://www.link-comm.com/squelch.html > > You did ask, so, I Hope this helps... > Kevin Custer Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
