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Greetings to the list,

I am just beginning to embark on a 2-meter repeater-building project, and
could use some advice. I need to keep out-of-pocket expenses minimal, and use
as much of what components I have on hand as possible.

I have several Mocom 70's, which I've been told are easy to tune but you have
to use two to make a repeater. I've found someone who has a manual, so I'll
have that within a week or two. I also have two GE Master Pro's that I've
also been told can be made into repeaters without much trouble.

As it stands right now, my options are leaning toward using two Mocom 70's
with a basic controller. Bells and whistles can come later -- most important
thing is to get the thing built and hopefully on the air when the weather
warms up enough to do the antenna work -- which is another thing: I need to
find a site for the repeater.

Any suggestions will be appreciated; thanks in advance.

73,
Jeff, W9SAR

<snipped for brevity>

Kevin,

Thanks for all the info. The Mastr Pro's are mobiles. I really don't see me
using those for the repeater. As I said, I think my best bet as things stand
right now is to use the Mocom's.

As for a controller, I'm looking at the NHRC mainly due to price, at least to
start. Not sure If I'll tackle the kit form or the assembled/tested (most
likely the latter) but I'm almost certain I'll go with one of these.

Thanks for the antenna suggestions. I'm going to try to go with seperate
antennas to avoid the $$$ of duplexers, but this will depend a lot on the
antenna structure. For example, if I have to go with a water tower, I'll need
to use a single antenna. But if I have vertical tower space, I'll be able to
go with two antennas. One question though: what are your thoughts on the
number of cavities in the duplexer? For example, a 6-cavity vs. a 3-cavity?
I know the 6 will cost more and provide more isolation, but at what point
would I need to decide which one?

Again, thanks!

73,
Jeff, W9SAR

Jeff, My thoughts are threaded below:

JHowel@... wrote:

From: JHowel@...

Greetings to the list,

I am just beginning to embark on a 2-meter repeater-building project, and
could use some advice. I need to keep out-of-pocket expenses minimal, and use
as much of what components I have on hand as possible.

I have several Mocom 70's, which I've been told are easy to tune but you have
to use two to make a repeater. I've found someone who has a manual, so I'll
have that within a week or two. I also have two GE Master Pro's that I've
also been told can be made into repeaters without much trouble.

Are the Mastr Pro's mobiles? If so the receivers are very good, but it's hard to
get the HV whine out of the transmitters audio. If they are stations running off
of a station supply, there is no problem.

As it stands right now, my options are leaning toward using two Mocom 70's
with a basic controller. Bells and whistles can come later -- most important
thing is to get the thing built and hopefully on the air when the weather
warms up enough to do the antenna work -- which is another thing: I need to
find a site for the repeater.

Any suggestions will be appreciated; thanks in advance.

73,
Jeff, W9SAR

The two M'70's should work fine. Micor's are really cheap right now since the
trend (even in ham radio) is turning toward using Mitrek's and Syntors (yes you
can make a repeater from a Syntor.)

I suggest a Micro Computer Concepts RC-100 (or RC-1000 if patch is necessary) they
are cheap and work fine. If you are into soldering things together to save money,
try the NHRC 4, I have one of these and it is great for the $75 I have in it.

A cheap repeater antenna is the Hustler G7-144 for 2M. Don't use a Cushcraft
antenna on your repeater like the ringo, or ranger. They have no decoupling of the
feedline and their pattern is horrible. The rf spewing from it will cause you (and
others) grief.

I like the WACOM duplexers. I have several sets for 2M and UHF and they really
work nicely.

Kevin

Kevin K. Custer W3KKC wrote:

A cheap repeater antenna is the Hustler G7-144 for 2M.

Kevin,

Do you (or anyone else) have any experience with the G6-270 (?) (the
dual-band G6) or the Comet antennas? This would be for relatively low
power duplex links. I understand the Diamond antennas are poor in duplex
operation.

Thanks,
Joe, KR3P

P.S. Kevin (or Dan), does the digest version work with attachments?

mch wrote:

From: mch <mch@...>

Kevin K. Custer W3KKC wrote:

A cheap repeater antenna is the Hustler G7-144 for 2M.

Kevin,

Do you (or anyone else) have any experience with the G6-270 (?) (the
dual-band G6) or the Comet antennas? This would be for relatively low
power duplex links. I understand the Diamond antennas are poor in duplex
operation.

Thanks,
Joe, KR3P

P.S. Kevin (or Dan), does the digest version work with attachments?

Hi Joe,

Dan and I have a few of the Comet and Diamond antennas in duplex service.
Some are in crossband duplex, and some are in same band duplex with all
bands duplexed. Some are a combination of both. I have never experienced any
duplexing problem with either brand.

We had a Diamond antenna (X-500HNA?) on the 147.105 Deep Creek Md. (Oakland)
machine for about two years. The antenna performed well except for
precipitation static because the antenna was top mounted. The antenna
eventually failed due to water ingress. I now heat shrink the joints before
installing this style antenna. I have availability to large shrink with an
inert sealant that is used to seal connectors on CATV hardline. It works
great for waterproofing Comets and Diamonds.

I have no experience with the G6-270.

The Digest version probably does not support html, that may be the VE6's
problem.

Kevin

hmm 3 cavities may should work ok 2 on tx one on Rx
might be able to get about 60 db isolation 6 cavities 3 rx 3 tx u could obtain
100db isolation which will greatly improve the repeater operations

JHowel@... wrote:

From: JHowel@...

<snipped for brevity>

Kevin,

Thanks for all the info. The Mastr Pro's are mobiles. I really don't see me
using those for the repeater. As I said, I think my best bet as things stand
right now is to use the Mocom's.

As for a controller, I'm looking at the NHRC mainly due to price, at least to
start. Not sure If I'll tackle the kit form or the assembled/tested (most
likely the latter) but I'm almost certain I'll go with one of these.

Thanks for the antenna suggestions. I'm going to try to go with seperate
antennas to avoid the $$$ of duplexers, but this will depend a lot on the
antenna structure. For example, if I have to go with a water tower, I'll need
to use a single antenna. But if I have vertical tower space, I'll be able to
go with two antennas. One question though: what are your thoughts on the
number of cavities in the duplexer? For example, a 6-cavity vs. a 3-cavity?
I know the 6 will cost more and provide more isolation, but at what point
would I need to decide which one?

Again, thanks!

73,
Jeff, W9SAR

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JHowel@... wrote:

<snipped for brevity>

Kevin,

Thanks for all the info. The Mastr Pro's are mobiles. I really don't see me
using those for the repeater. As I said, I think my best bet as things stand
right now is to use the Mocom's.

As for a controller, I'm looking at the NHRC mainly due to price, at least to
start. Not sure If I'll tackle the kit form or the assembled/tested (most
likely the latter) but I'm almost certain I'll go with one of these.

I'll build the NHRC4 for you.

Thanks for the antenna suggestions. I'm going to try to go with seperate
antennas to avoid the $$$ of duplexers, but this will depend a lot on the
antenna structure. For example, if I have to go with a water tower, I'll need
to use a single antenna. But if I have vertical tower space, I'll be able to
go with two antennas. One question though: what are your thoughts on the
number of cavities in the duplexer? For example, a 6-cavity vs. a 3-cavity?
I know the 6 will cost more and provide more isolation, but at what point
would I need to decide which one?

Again, thanks!

73,
Jeff, W9SAR

-

The number of cavities needed really depends on several things. First and foremost
is the size of the can itself. My Wacom plexers are made from 8" diameter tubes.
The larger the diameter the higher the Q and therefore (@ narrow spacings I.E. 600
kc.) the easier to retain the notch depth. It is harder to get deep notches @ 600
kc with small diameter cans. When you bring the notch closer to the pass frequency
(in any duplexer) the notch will start to affect the pass insertion loss, and the
notches depth. The larger the can the lesser the affect on pass and notch at
narrow splits. Many feel the fact that uhf duplexers are smaller is due to
frequency. This is true to a point. The bigger reason (in scale) is due to the 5
meg split used. A smaller diameter (Q) duplexer can be used at this wide tx to rx
spacing and still provide big notch depths.

It may take 6, 5" cans to equal the isolation of 4, 8" cans.

Also one has to take into account the radio situation that the duplexer has to
satisfy. If your receiver is deaf with .5 uV of sensitivity, the duplexer doesn't
have to work very hard to make duplex work. On the contrary if the receiver is say
.15 uV sensitivity, the duplexer has to be able to isolate the extra receive
ability of this receiver (approx. 10 dB).

And then there is the transmitter. Noisy Transistor transmitters take more
isolating ability to duplex. Yes, in most cases the tube type transmitters are
made duplex more easily. For more about this thread go to


Hope this helps,

Kevin