be
iffy for me.
Sorry to take up the bandwidth on this topic here, but I felt this was the
best way to wrap it up.
Bob NO6B
last year of organizing a private charter from (I think)
Prescott AZ direct to Dayton.
Bob NO6B
of the exciter so you don't have to deal with this delay
yet still not have the TX signal heard near the site.
Bob NO6B
rear ended my friend who was driving..
I've stayed there 5 times never had a problem. At less than $30/night
for a week w/fridge microwave, I don't expect much else other than no
bedbugs/loud neighbors/dirty rooms.
Bob NO6B
oscillator, there may be little harmonic content generated on the board.
Bob NO6B
whiskers, I took a pic of the
helical resonator cover plate of the last MVP I had to service for this
problem.
Bob NO6B
configuration. Both should be
reliable enough for your application, but you can inquire with each
manufacturer as to the absolute operating temperature limits.
Bob NO6B
.
Bob NO6B
knockoff at the swap meet a few years ago that was
obviously a 430-440 cut antenna even though it was labeled 440-450, as it
had very high reflected power at the top end of the band. Perhaps that is
what you had.
Bob NO6B
available.
Maybe it's the drop in the value of a US dollar? I think
US Dollar to Candadian Dollar conversion rate is close to 1:1 now.
The main reason why I stopped using West Crystal. They didn't raise their
prices, but they got too expensive.
Bob NO6B
in the 440-450 MHz
range or are only off by a small amount - maybe 1.8 dB loss instead of 1.5 dB.
I'd say go for it. If there is excessive insertion loss it can be easily
measured with a synthesized TX, isolator, wattmeter 50 ohm termination.
Bob NO6B
diplexer performed much better.
Bob NO6B
. Since the output matching
circuitry is probably designed for best match at full output power, I'd
imagine that mismatch losses would go up as the output power is
decreased. That would also partially explain the lower efficiency at
reduced output power.
Just brainstorming...
Bob NO6B
a couple vhf and uhf exec II receivers that tuned up nicely in the
.19~.2uv range so I think I'm doing/reading it correctly.
A UHF Exec II with 0.2 µV 12 dB SINAD sensitivity? Must have a preamp in
front of it.
Bob NO6B
voice audio.
Another solution is to install a bottle of helium with a dispensing tube
run up the mic cable with a solenoid valve activated by the PTT switch ;)
Bob NO6B
developed replacement LCD
displays for some of the old yet popular instrumentation, for example the
HP8720 VNA: http://www.ntecusa.com/sales/dsp_model.cfm?modelID=21273. I
wonder what it would take to develop such a retrofit for the older IFR
monitors?
Bob NO6B
.
KG Electronics (http://kgelectronics.com) specializes in IFR-1200
repair. He says he'll also service 1500s. I've yet to use his services,
but plan to once I start having problems with my A7550. Undoubtedly much
cheaper than Aeroflex. He won't work on COM120Bs though.
Bob NO6B
occasional usage by non-members for purposes of
test-driving the system or to simply say hi. This is good IMO as it
gives noobies more repeaters to try without risk of being chewed out for
intruding on someone's private frequency.
Bob NO6B
not be a
need to use a frequency that has a repeater output. I listen/scan the
basic simplex frequencies and usually hear one or two conversations a
week. Most of the simplex frequencies never are used.
Exactly.
Bob NO6B
there were 2 pairs available for
them, but were removed due to lack of any interest in the mode.
Bob NO6B
few apparently go
the direct COS route with this radio.
Bob NO6B
Anyone have any leads on the above? I can try calling Duracomm tomorrow,
but from what I've read they aren't very helpful in this area. Thanks.
Bob NO6B
At 8/3/2009 14:42, you wrote:
Or RG-9/U.
Norm N5NPO
I think most RG-9/U has copper braid, is unsuitable for use in any
duplexed portion of a repeater system (from the duplexer T to the
antenna). Should be OK for RX TX interconnects though.
Bob NO6B
- Original Message -
From
has the
UHS preamp installed in the RX is used in the middle of downtown LA -
zero IMD or desense.
Bob NO6B
could try a pair of commercial HTs, but the duplex ability of this unit
depends on the filtering of the helical resonators in the RX. I tried
swapping out a pair of amateur-grade HTs (Icom IC-32AT Alico G5T) for the
MVP, got severe desense.
Bob NO6B
. Positioning the bays around a
central supporting mast of a UHF array creates considerable pattern
distortion and gain is lost.
I once modeled this arrangement in NEC-Win: the resulting pattern looked
like a warped pancake. On-horizon gain was all over the place.
Bob NO6B
channels and everyone is still using NBFM as they have for the past
nearly 40 years?
The latter. Not narrowbanding at all, just an attempt to more effectively
utilize the spectrum using existing bandwidths.
Bob NO6B
At 8/9/2009 16:41, you wrote:
What was the spacing between the tower legs at the mounting location of
the dipoles in your model?
No tower. Only the rooftop-mounted mast 4 dipoles, which is what I was
using at the time.
Bob NO6B
notch-only duplexers like the DB-4048 that are made for 600
kHz spacing. Spec'd notch depth is only 80 dB which can be a bit short,
especially for solid-state multiplied source TXs (as opposed to tube-type
or PLL-sourced).
Bob NO6B
at 600khz above the notch.
With them, the total loss is about 2 - 2.5dB.
Bob NO6B
At 8/10/2009 20:59, you wrote:
I guess I'm still looking for an answer to the original
question. Do the notch cavities work @600khz spacing?
The specs I gave for the DB-4050 were at 300 kHz spacing. At 600 kHz, the
loss goes down to 1.5 dB.
Bob NO6B
ANDed with the COS would take care of that.
Bob NO6B
care if I
lose users that are incapable of properly modulating their radios.
A simple VOX ANDed with the COS would take care of that.
Bob NO6B
I would be interested in a description of the above...
Any ol' audio detector/filter/comparitor would do. Nothing fancy like the
SmartVox we use
the past 5 seconds was at
least 1.5 kHz.
Bob NO6B
What action does the above circuit take?
It would be ANDed with the COS, so that anyone too soft-spoken would drop
out of the repeater.
We had one repeater around here with that feature. AFAIK it worked quite
well. It was removed when
in the day when the VOX was in
place. So I'd say most were well trained, the few that left probably
gave the lesser-used low-level repeaters more use. Win-win.
Bob NO6B
At 8/14/2009 17:54, you wrote:
Sounds like, in essence, it was a closed repeater. Only those meeting some
tough standards were allowed.
Oh, it was very open. How tough can it be to simply speak up?
Bob NO6B
can still almost
eliminate the squelch tail with an ADM.
Bob NO6B
At 8/21/2009 16:16, you wrote:
Because CTCSS falses on the random noise.
Been there, done that, gave away the t-shirt.
A GE Versatone decoder won't false. IMO only defective CTCSS decoders
false on white noise.
Bob NO6B
a DMax close to 4.0. I think my 4870 is around 3.8.
Bob NO6B
the antenna noise temperature is
usually much lower than 300 K, so in those cases yes you want to minimize
all loss between the antenna RX.
Bob NO6B
=2scid=12. At
this point the SCom is a better value for the money (3 ports vs. 2 on the
RLC-1+, costs a bit less than the RLC-1+), but the RLC-1+ has more
functionality at this time, as the 7330 is in an early stage of firmware
development.
Bob NO6B
needs to be modified (installing 2 jumpers in the control
head). Download the FT-5200 manual via a Google search for FT-5200
manual, then see p. 37. You might check pin 5 of the mic connector for a
COS signal in case someone already performed the mod. on the radio.
Bob NO6B
) band.
Bob NO6B
plans show something like repeaters in this area all use
CTCSS tone X I always cringe a little.
Sure makes it a lot easier for travelers to find all the local repeaters.
Bob NO6B
At 8/30/2009 09:57, you wrote:
When area plans show something like repeaters in this area all use
CTCSS tone X I always cringe a little.
Sure makes it a lot easier for travelers to find all the local
repeaters.
Bob NO6B
Who's so dumb that they SCAN with CTCSS Decode turned
use a
different CTCSS tone accept the fact that the repeater's performance will
be severely degraded when this happens.
Bob NO6B
, but then again why take the chance
on a short jumper where loss isn't an issue? Silver-plated RG-214, RG-393,
RG-223, RG-400, or RG-142 is known to be safe for that application.
Bob NO6B
, with RG-214
jumpers between the hardline duplexer/antenna.
Bob NO6B
Corey N3FE
On Mon, 31 Aug 2009 11:46:36 -0400, Chuck Kelsey
wrote:
Sounds like maybe a bad antenna. Don't use the foil/braid cable anywhere in
a repeater system.
Chuck
WB2EDV
- Original Message
isolation
specs. The old sheet lists the finish as gray enamel, while the new ones
are black enamel.
Guess they really don't make them like they used to.
Bob NO6B
P.S.: I'm hanging on to the old sheet; when I get some time I'll scan it
send it in to Mike for posting to the R.B. page.
At 9/2/2009 15:17, you wrote:
The antenna is on the top of a small wooden storage building.
A mast is placed up against the peak of the roof, and the 224
is on top of that.
What's in the building? Any (loose, rusty) metal objects inside?
Might also try a different antenna.
Bob NO6B
.
Can anyone confirm the above?
Bob NO6B
in the duplexer.
Bob NO6B
channel,
and the 310 kHz
reference is an approximation.
Can anyone confirm the above?
Bob NO6B
You're trying to make it easier than it is Bob :-)
Normally it would be 309.440559 kHz above the bottom of the channel. That's
a real big normally.
OK, thanks. Well as long as they don't
turn the TX off
on while listening to the local audio you could hear any desense, but you
don't need repeat audio for that.
Bob NO6B
than
silver-plated will likely eventually cause desense, not only to your
repeater but possibly others as well.
Bob NO6B
come close to
matching the 7/8 in line loss.
Not true, if we're talking N connectors. N connectors are virtually
lossless at UHF lower frequencies. 2 2 ft. RG-214 jumpers are around 0.2
dB loss, less than the difference between 100 ft. of 1/2 7/8 hardline @
450 MHz.
Bob NO6B
=item35a37f3c02_trksid=p3286.c0.m14http://cgi.ebay.com/GE-MASTR-II-UHF-Receiver_W0QQitemZ230376291330QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item35a37f3c02_trksid=p3286.c0.m14
How do we know it's an 88-split UHF (450-470 MHz)? It could be 470-494 or
494-512 MHz.
Bob NO6B
mobiles go for that much
at the local swap meets.
Bob NO6B
ports.
Bob NO6B
is
causing a mix.
Bob NO6B
radio's TX look like 50 ohms.
Bob NO6B
. If not, it's possible the
interstage tuning (1st stage output 2nd stage input) are fixed-tuned,
which explains the narrow tunability.
Bob NO6B
is that the interstage tuning is fixed, which would explain
the low bandwidth.
Bob NO6B
a wide (2.5 MHz or greater) split a mobile duplexer. Then the
antenna separation becomes 0.
Bob NO6B
at least 80
dB. Possibly with a very low noise (PLL exciter) TX you could get away
with a few dB less but ~67 dB isn't enough. But as you say, using this
split antennas just a few feet apart might yield sufficient isolation.
Bob NO6B
the
horizon so users close to the system but behind some local minor
obstruction wouldn't lose coverage. Not sure what happened to the
company. I do see some other manufacturers use that term, but only for
antennas above 700 MHz.
Bob NO6B
meters but still to this day there is a 220 repeater that
should cover the whole course, in fact can be heard solidly along the
whole route, but has a deaf RX apparently the owner doesn't want to fix
it. So we ignore it use our own system installed specifically for the event.
Bob NO6B
?
In a word, bad. The RXs are salvageable, do have some strong
points. The internal squelch is NG IMO needs to be replaced, preferably
with a Micor squelch. The TXs internal controller are junk.
Best bet for 220 is a converted GE or Micor, or find a Midland 13-509 to
split apart.
Bob NO6B
to listen to. - Mike
Wondering what you did to it to make it sound so good. Every one I've
heard around here sounds very restricted somewhat distorted. In fact, I
can usually tell if a repeater is a Kendecom by the characteristically poor
repeat audio.
Bob NO6B
lots of DC current at between 5 to 8 volts. Yes I
had the polarity correct.
A small protoboard comes in handy for this sort of test; you can plug a
whole batch in, wired in parallel, test them simultaneously.
Bob NO6B
IF
amplifier overload). A 10 kHz LPF in front of the Micor squelch board may
cure that problem.
Bob NO6B
.
Maybe there's something about the Micor I'm missing that others love.
How about 2 millisecond decay time on strong signals? Even many
controllers don't sample the COS line that fast.
Bob NO6B
in percent is much smaller at 2 meters than at
6. At 6 meters, the spacing is just under 1% of the operating frequency,
while at 2 meters it's only 0.41%, so the required Q of the 2 meter
duplexer will be more than double what's required @ 6 meters.
Bob NO6B
At 10/22/2009 08:06, you wrote:
Bob,
Have you got a diagram or notes on how you did your installation?
Unfortunately, no. It was done for a friend's repeater that was partially
stolen (including the RX); the remaining pieces were sold.
Bob NO6B
suspect this to be due to design flaw in the MR4 design (mid-stage IF
amplifier overload). A 10 kHz LPF in front of the Micor squelch board may
cure that problem.
Bob NO6B
Funny you should mention that, Bob... The Kendecom repeater the local
club had would indeed overload. If you were within
the signal at all, an ADM set to a long delay can turn
those muted valleys into muted peaks, creating a problem with the squelch
where none existed before.
Bob NO6B
of RG400 vs Superflex
is negligible, but a poorly installed connector will cause a big difference.
I use RG223 for my TX RX jumpers unless I need more than 2-3 ft. it's
for UHF, then I go to RG214. RG223 is a bit more flexible than RG400.
Bob NO6B
need much
CTCSS or exactly the right frequency to get through. It was easy to tell
who's CTCSS encoders were off frequency, injected into the mic input, etc.
by all the courtesy tones going off during the users' transmissions.
Bob NO6B
!
Bob NO6B
).
If you do get desense when the cables are near each other, it might
indicate RF coupling to the outside of the coax from the TX or RX. This
indicates a bad/improperly installed connector, or shielding problems at
the TX or RX.
Bob NO6B
. The somewhat older 742
doesn't like any of them. But believe it or not, the old TK-801 repsonds
to the 7330 at 180 degrees, but I haven't heard it work with anything
else, even the factory Micor...
WD8CHL
The TK-805D's decoder works with the Mastr II's CG reverse burst.
Bob NO6B
a lot more of it.
Heh, I can see it now: hackers spelling out messages on the faces of
buildings by hacking into the lighting controls.
Bob NO6B
that comment on legality.
Neither do I. IIRC ACSSB is nothing more than SSB with companding a
pilot tone. The latter doesn't make the former a totally different mode.
Bob NO6B
don't go looking for them anymore. I
prefer using Mastr II or MVP RXs now.
Bob NO6B
of the 522-509. So I made a cable of the right
length (1/2 wavelength?) to connect that cavity to the TX port. After
tuning I got ~90 dB on both TX RX.
If you don't have a pass-notch can available, you might get enough
isolation by adding a pure pass can to the TX port.
Bob NO6B
both the homework and
technical work.
It's a lot more expensive and sad to think a lot of
equipment is being replaced, when other viable options
are available.
s.
I'm not too disappointed, since us hams will be the beneficiaries.
Bob NO6B
be disposed of. When it's sold back into service, the
hazardous/toxic waste issue disappears.
Bob NO6B
to 144.39. Tried a couple of exciter boards until we
found one that made it down. If it's the RX you're having trouble with
make sure you follow the pre-tuning instructions in the manual.
Bob NO6B
At 11/21/2009 18:13, you wrote:
there were 5. kahn ISB, motorola CQUAM, belar, harris, and magnavox.
Do one of these cause a rubber band sound when listening off channel (+/-
10 kHz)? There's an AM station in Needles (KTOX 1340) that does this -
very weird sounding.
Bob NO6B
ago, so maybe some other AM stereo
modes were in use at the time.
Bob NO6B
Anyone got one they want to get rid of?
Please reply directly to no6b at no6b dot com. Thanks.
Bob NO6B
of those to 220 by cutting down the center tube - wish I
had some of those now.
Bob NO6B
.
Not if you use a good receiver, or not use a preamp with too much gain.
Bob NO6B
-limited VHF bands, but in SoCal on 220 440 it
is. The only place I'd use a GLB preselector would be a space-constrained
application where a 1/4 wave resonator simply couldn't fit.
Bob NO6B
pick up 1.5 dB.
Note that the pass filters that Chip sells at
http://anglelinear.com/filters/coax_filters.html are only 0.3 to 0.4 dB
loss per cavity. A bit pricey IMO, so I look for something used.
Bob NO6B
C921 with a
smaller value cap to reduce the low frequency content of the step.
Bob NO6B
- the stock sensitivity of an MVP or Mastr II is perfectly
matched to our environment. I have noticed that away from this area, the
noise floor on 2 meters can be much lower.
Bob NO6B
At 11/26/2009 09:39, you wrote:
You might need to add a several DB attenuator
between
the pre amp and the receiver to keep from over
driving
the front end.
Not if you use a good receiver, or not use a preamp with
too much gain.
Bob NO6B
What defines too much gain
and a notch cavity with the
preamp.
How much isolation do you get out of the duplexer? If it's less than 80
dB, you might need additional filtering on the TX, since phase noise is the
usual cause of desense when duplexer isolation is insufficient.
Bob NO6B
a filter placed AFTER the active device help improve it's
P1dB? It may protect the receiver(s) downstream, but they do nothing to
improve the power-handling performance of the preamp/preselector.
Bob NO6B
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