Subject: Re: [Repeater-Builder] Re: Repeater receiver testing
yes I know -55db is I think around 399 microvolts which will flatten any
receiver,
I sure hope not; there are many signals coming down my antenna that are that
strong. In fact, my 440 repeater 13 miles away is at about
Kevin, I'm sorry to have to tell you this but I think your
calculator batteries need to be changed.
0 dBM = 0.2236 volts in a 50 Ohm circuit.
+20 dBM is indeed 100 mW and P=EI and inserting 100 mW into
the Eq. for Volts in a 50 Ohm system, E= the sq. rt. of the
quantity (.100 x 50) =
mistake. It's time for a new calculator for me.
And then the computer crashed. Time for a new computer too.
AC
From: Jeff DePolo j...@broadsci.com
To: Repeater-Builder@yahoogroups.com
Sent: Tue, July 27, 2010 11:09:55 AM
Subject: RE: [Repeater-Builder] Re: Repeater
allan crites wrote:
Kevin, I'm sorry to have to tell you this but I think your calculator
batteries need to be changed.
0 dBM = 0.2236 volts in a 50 Ohm circuit.
+20 dBM is indeed 100 mW and P=EI and inserting 100 mW into the Eq.
for Volts in a 50 Ohm system, E= the sq. rt. of the quantity
Sent: Tuesday, July 27, 2010 10:05 AM
Subject: Re: [Repeater-Builder] Re: Repeater receiver testing
I sure did. Thanks to you Jeff for your response and my sincerest apology to
Kevin.
I did the calculation four times and got the same wrong answer four times
before I hit the send
At 7/27/2010 10:29 AM, you wrote:

Get a Mac. Much more efficient and crash free..
At the last coordinators' meeting I attended there was one laptop crash...
Yup, it was a Mac ;)
Bob NO6B
At 7/27/2010 10:15 AM, you wrote:
case you haven't figured that out)). By the way, the GE PLL exciter has
22 dB less phase noise at 600 kHz from its primary carrier than does its
multiplier counterpart, you can bet it's way more than that at 6 MHz.
That 22 dB is an interesting figure: the
Yep, Mac's crash all the time. They get virus' too.
Chuck
WB2EDV
- Original Message -
From: n...@no6b.com
To: Repeater-Builder@yahoogroups.com
Sent: Tuesday, July 27, 2010 9:38 PM
Subject: Re: [Repeater-Builder] Re: Repeater receiver testing
At 7/27/2010 10:29 AM, you wrote:

Get
tahr...@swtexas.net
To: Repeater-Builder@yahoogroups.com
Sent: Monday, July 26, 2010 12:06 AM
Subject: Re: [Repeater-Builder] Re: Repeater receiver testing
Hi Steve,
I measured each way to the common point... RX to antenna
Tx to antenna, and each one had a notch of about 102dB
Good thoughts Milt, and I'll add a few
While not an easy thing to find I would suggest that you most likely
need some sort of a bandpass cavity on the receiver to protect from
the noise that gets past the heliax notches.
Remember that a notch duplexer only removes the notched
portion
At 7/25/2010 15:54, you wrote:
Hi Jeff
yes I know -55db is I think around 399 microvolts which will flatten
any receiver,
I sure hope not; there are many signals coming down my antenna that are
that strong. In fact, my 440 repeater 13 miles away is at about that level
at my antenna connector.
Hi Jeff,
Thanks for the info. any idea about the complexity
of the 'summing' device? Can I do with a resistor combo,
then perhaps sub some from the actual generators' output?
Tim
--- In Repeater-Builder@yahoogroups.com, Jeff DePolo j...@... wrote:
The holy grail for FM performance
yes I know -55db is I think around 399 microvolts which will flatten
any receiver,
I sure hope not; there are many signals coming down my antenna that are
that strong. In fact, my 440 repeater 13 miles away is at about that level
at my antenna connector.
Reminds me of a test I
If you are attempting to verify a manufacturer's specification, the TIA-603
procedure should be used. If you are serious about that, you should probably
acquire TSB-88 in addition to TIA-603.
Here is a link to a presentation that discusses adjacent channel testing and
explains the roles of
Hi Nj902,
Well, I'm not trying to be exacting in the measurement, I'm just trying to
track down a desense issue in the system. I figured I'd look at how
the receiver does with the adjacent (transmitter) signal injected directly
into the rx input port.
The spectrum analyzer hooked up to the RX
To: Repeater-Builder@yahoogroups.com
Sent: Sunday, July 25, 2010 9:24 PM
Subject: [Repeater-Builder] Re: Repeater receiver testing
Hi Nj902,
Well, I'm not trying to be exacting in the measurement, I'm just trying to
track down a desense issue in the system. I figured I'd look at how
The issue for repeater receiver desense is the same basic issue that affects
the bench test. For the bench test if the generator used for the adjacent
channel signal has too much phase noise - that noise will degrade the receiver
before the carrier level can be raised to the manufacturer's
Hi Steve,
Running 80 watts into the duplexer, getting 50 out.
Getting about 102dB notch out of the duplexers.
From a previous thread a couple of days ago, the
consensus was that -50 was fine for this receiver.
I hooked up my IC-706 to the TX port, and even
at 5w, I was getting significant
Hi 902,
Understand about the sideband noise, but I figured at a MHz away, it
probably wouldn't be an issue. Getting the same performance out of
both sides of the duplexer ... about 102dB notch 1.5dB attenuation.
Using RG142 for all interconnects, except from TX/RX to duplexer, and
those are
Been following this thread for a while, some thoughts in random order:
If I remember correctly you said that you are using the 1 5/8 heliax
notches as your duplexer.
If I also remember correctly others have reported problems of many
sorts with these homebrew devices.
While not an easy thing
25, 2010 10:28 PM
Subject: [Repeater-Builder] Re: Repeater receiver testing
Hi 902,
Understand about the sideband noise, but I figured at a MHz away, it
probably wouldn't be an issue. Getting the same performance out of
both sides of the duplexer ... about 102dB notch 1.5dB attenuation
Hi
you beat me to it, I would suggest a duplexer problem as -55dB
isn't a lot you should have ideally better than 80dB. It also could be
the fact that you are running too much tx pwr, have you tried dropping
it down.
73
Steve, M1SWB(UK)
He said he measured the Tx carrier at the Rx
. We are limited to 25w erp so usual
tx in is about 25w and out of the duplexer around 20w
73
Steve
- Original Message -
From: Tim tahr...@swtexas.net
To: Repeater-Builder@yahoogroups.com
Sent: Sunday, July 25, 2010 10:23 PM
Subject: Re: [Repeater-Builder] Re: Repeater receiver testing
an isolation test with sig gen and analyser
73
Steve
- Original Message -
From: Jeff DePolo j...@broadsci.com
To: Repeater-Builder@yahoogroups.com
Sent: Sunday, July 25, 2010 11:43 PM
Subject: RE: [Repeater-Builder] Re: Repeater receiver testing
Hi
you beat me to it, I would suggest
Hi Jeff
yes I know -55db is I think around 399 microvolts
No, you're still missing it. He said -55 dBm (m = milliwatts), not -55 dB.
which will flatten any receiver
-55 dBm at 1 MHz offset isn't going to bother any half-decent receiver. A
decent receiver would have 100 dB of
Tim,
It appears to me that your measurement procedure is correct - and that the
results you have gotten would normally be sufficient isolation to allow
desense-free duplex operation.
If you have some attenuators available - or better yet - a switchable [in 1 dB
increments] attenuator - there
Hi Nj,
Thanks for the info. That's one test I'll be trying tomorrow.
I did a bit of snooping in the IF chain with a scope probe
my spectrum analyzer, and found that at the back end of the
xtal filter chain/amplifiers, I saw two signals, one a MHz above
the desired receive frequency, and it was
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