Hello Kevin
Thanks for your reply. Your statement is correct in that all of the
receiver coils begin to tune at the bottom of their travel. I have even tuned
two or three too far and they dropped out with the resulting work to retrieve
the screws. When tuned as best I can for sens the s/n ratio is 1+uv at 12db
sinad. The original frequency sens was less than 1uv-usually about .3uv for
12db sinad. Replacing the coils are about the only solution I know of for
these high split VHF units. I have in the past replaced two sets of receiver
coils with Motorola coils and found I have good sensitivity as before
modification. The transmitters all tuned well on this split and gave rated or
more power output.
The Mitrek coils looked very much like the Micor coils. I have replaced
probably a half dozen Micor receiver coils proscured from Motorola in the past
20 or so years. Thanks. 73 de Tom Manning, AF4UG
----- Original Message -----
From: Kevin Custer
To: Repeater-Builder@yahoogroups.com
Sent: Thursday, December 18, 2008 10:02 PM
Subject: Re: [Repeater-Builder] Holiday Special - MICOR 2 meter receiver
conversion from W3KKC
Tom,
You say you find similar operation on 4 or 5 units. By that do you mean they
won't make book specification on any frequency below 146 MHz? If that is the
case, I would believe something is wrong. I have seen many Mitrek high-band
receivers that were tuned for 144 something and had very good sensitivity.
Let me ask you this.... When tuned at 144.89, is the front-end tuning all
"one ended", or is there adjustment to spare? In other words, can you tune the
front-end without the fear of the tuning screws falling into the casting? If
you have room left to go lower in frequency, then the front-end is not the
problem, and you'll need to look elsewhere for the lack of sensitivity.
Another question - do these 4 or 5 units tune and make book spec sensitivity
on their original high-band channel?
I guess what I'm saying is I doubt the problem is the front-end helical
resonators, but if there is a need for a conversion I'm not opposed to looking
into making a modification available, if it is needed. If there are others on
the list that have had good luck with the Mitrek on frequencies below 146 MHz,
please chime in and let us know what you have and how well it works.
Kevin
Hello Kevin
You are correct on your freqs for xmit and rcv. The Mitrek units I
have will only tune receive to 146.00Mhz. This leaves more than one meg to go
to meet tolerance on 144.890. I have tried 4 or 5 units and find similar
operation of all. This is the reason for my question about the Micor coils
working for Mitrek. Thanks. 73 de Tom Manning, AF4UG
----- Original Message -----
From: Kevin Custer
To: Repeater-Builder@yahoogroups.com
Sent: Tuesday, December 16, 2008 8:44 PM
Subject: Re: [Repeater-Builder] Holiday Special - MICOR 2 meter receiver
conversion from W3KKC
Tom,
Do you mean 144.89 MHz? I would think your repeater would *transmit* on
145.490 MHz.... At any rate, no conversion is necessary for the Mitrek to make
book specification sensitivity on 144.890 MHz.
Kevin
Good afternoon Kevin
My need is to convert two or more Mitrek receivers to cover
145.49Mhzz, which is our receive freq for our repeater. Thanks. 73 de Tom
Manning, AF4UG
----- Original Message -----
From: Kevin Custer
To: Repeater-Builder@yahoogroups.com
Sent: Tuesday, December 16, 2008 12:19 PM
Subject: Re: [Repeater-Builder] Holiday Special - MICOR 2 meter
receiver conversion from W3KKC
Tom Manning wrote:
Good morning Kevin
I have a question. Will these coils also work in a Mitrek?
Thanks. 73 de Tom Manning, AF4UG
Hi Tom,
To answer your question, the conversion will not work in the Mitrek.
Unlike the MICOR, the Mitrek high-band unit that is most common has a
lower tuning limit of 146.00 MHz as specified from the factory. This means
that the units normally tune anywhere in the 2M ham band without modification.
What frequency do you need to listen on?
Kevin
