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Posted: 8/12/2007 7:19:08 PM EDT
I just got a friend into the hobby and we've been experimenting with FM Simplex between our houses (about 2 miles apart).

I loaned him my VX-6R along with a 19" flexible whip and a mag mount antenna.

On my end with our experiments I've used an FT-8800M Mobile (Comet SBB-5 on NMO hard mount) and my FT-857D Base (Comet GP-3 on mast just over roof level outside).

What works:
We have good communication thru several repeaters, UHF simplex (446.000), and I hear him *fine* on about every antenna and power combination he's tried.

What doesn't:
He has garbled copy from me on 2m Simplex. We've tried every bit of the 2m simplex band plan in 15 kHz steps. Says my sig is very strong but I sound garbled like talking through a paper cup or Charlie Brown's teacher. We've had this problem with me TX'ing on both rigs mentioned anywhere from 5w to 50w. Increasing power helps some, but not completely.

What's weirder:
He can copy me *fine* by tuning off my op freq 5kHz either direction. If I'm on 146.550, he copies me better on .545 and .555.

Initially I thought I was competing with interference at his location, BUT we tried one other thing -- (briefly) operating simplex on the output freq of a local repeater. He said it sounded fine then. And how would his "tuning off" by 5kHz improve the clarity of my signal?

I haven't changed anything on my rigs from before we started, and I use them both regularly (granted, for repeater work mostly) without any such complaints. He's new so he might not be able to identify what he's hearing by the sound of it.

Thanks for reading and any suggestions you may have.
Link Posted: 8/12/2007 8:06:28 PM EDT
I would double check that you are transmitting in FM mode. Sounds like the radio on your end may be in AM or SSB.

--Scott
Link Posted: 8/12/2007 8:14:35 PM EDT

Initially I thought I was competing with interference at his location, BUT we tried one other thing -- (briefly) operating simplex on the output freq of a local repeater. He said it sounded fine then. And how would his "tuning off" by 5kHz improve the clarity of my signal?


Check to see if HIS radio is RECEIVING on AM/SSB. (I'm not familiar with the characteristics of his radio.)


Also, sometimes this problem can be caused by "over-deviation." Basically, you are overdriving YOUR microphone by speaking too loudly into it.
Link Posted: 8/12/2007 8:52:56 PM EDT

Originally Posted By GlockTiger:
He can copy me *fine* by tuning off my op freq 5kHz either direction. If I'm on 146.550, he copies me better on .545 and .555.


first off, kudos to you for including a lot of equipment info in your post, and also detailing what experiments you ran and their results.

although the VX6R will RX in AM, FM, and WFM mode, unless you are in an FM mode you won't hear the local repeater at all.

this issue sounds suspiciously like one of two things:
(a) overdeviation at the TX end, or
(b) the VX6R inadvertently got set to NBFM ("HALF DEVIATION") while in VFO mode.

i somehow doubt that overdeviation at the TX end is the issue, since it appears with both the FT8800 and the FT857 doing the talking. it's very unlikely that both radios would be hot. it's also unlikely that the same mic is used with both radios, so that rules out an issue with the mic element as well.

so let's go with this theory for a moment...

your friend is probably tuning to the repeater via the VX6R's memory mode.
however, for simplex, he is using VFO mode.

it may be the case that since each memory location sets a lot of the radio's parameters, TX from the VX6R to/from the repeater has the correct deviation. however, switching to VFO mode, you may find that the radio is set for "HALF DEVIATION". see the bottom of page 83 of the VX6R user manual for details on how to check/change this. half deviation is used for MURS and FRS/GMRS, for example, as allocated channels within those bands are quite close together.

losdos.dyndns.org:8080/public/ham/yaesu-vx6r/VX-6R_UserManual.pdf

hope all that leads to a solution.

ar-jedi
Link Posted: 8/12/2007 9:55:58 PM EDT
[Last Edit: 8/12/2007 9:57:17 PM EDT by Gamma762]

Originally Posted By ar-jedi:
Originally Posted By GlockTiger:
(snip)

This is the problem, the receive mode on 2m on his end is not correct, probably in AM receive, or else narrowband (12.5kHz) mode.. When he changes to 440 or memory channels the mode is correct.
Link Posted: 8/13/2007 2:24:14 AM EDT
That is very strange. I'd get a third ham to loan equipment to him,
and then you, to pin down which side the problem is on, and go from there.

Link Posted: 8/13/2007 2:46:09 AM EDT
[Last Edit: 8/13/2007 3:00:45 AM EDT by EXPY37]
Check to be sure he isn't in AM mode, because if he is, the fact that he copies better a few kc higher or lower sounds like he is demoding your signal using the old tried and true "FM slope detection". [In the old days of downconverters feeding AM broadcast band radios to receive FM police, etc, xmissions, it was commonly used with good performance]

From your info about tuning BOTH up OR down 5kc, it would be a good bet, almost a certainty.

It doesn't sound like his radio is set to a narrower or wider FM mode because the IF filter BW and FM demod in the 'R7 is the same, the audio gain is set higher or lower but the IF filter is the same IIRC. [I could be wrong about this, I don't have a manual handy.]

Link Posted: 8/13/2007 5:24:51 AM EDT
Thanks much guys for the ideas!

I like the theory that he may have set the VX-6R to a different mode in 2m VFO while it may be correct on memory channels and UHF. His sig back to me sounds great, so I wonder if it momentarily defaults back to FM when PTT is pressed, and when released goes back to AM / WFM?

Anyhoo, we'll hit that idea first this evening before trying other things. I have a few more tricks to try that we haven't been able to do yet: have him go off-site from his home, try one more radio on *my* end (just in case it's TX related), and a few other things.

Thanks again, y'all.
Link Posted: 8/13/2007 6:38:02 AM EDT

Originally Posted By GlockTiger:
His sig back to me sounds great, so I wonder if it momentarily defaults back to FM when PTT is pressed, and when released goes back to AM / WFM?

Yes, since the radio doesn't transmit in AM or WFM modes. The same thing happened to me once with an FT530, one of the VFOs got onto AM mode and it drove me crazy until I figured it out. Pretty good bet that is what is happening.
Link Posted: 8/13/2007 5:46:31 PM EDT
Yeeha! Told my buddy to press the "mode" button until it scrolled thru to "Auto" and situation resolved! He and I had a good experiment this afternoon and we established 2m contact -- he was on 5w (VX-6R) and I was on 1.5w (VX-2R).

Now since my original issue is solved, I'll hijack my own post -- I have concluded that my Comet SMA-503 STINKS.

It truly performs worse than the stock duck on both my VX-6 and VX-2. Waste of $30. I know antenna performance is highly relative and others have had different results, but I thought based on the eHam reviews it would be a worthwhile addition. I cannot recommend that one though.

One that I CAN recommend (still my best HT antenna) is an $15 Opek 17" (approx) whip.


HR-603VU

Dual Band Rubber Duck HAM Antenna

* FREQ: 2M / 440MHz
* Whip: Shape Memory Alloy
* SMA Plug (Gold-Plated)
* V.S.W.R.: less than 1.5
* Overall Length: 16 1/2"
* MSRP: $15.00


It's basically a copy of Comet's SMA-24 that I picked up at a hamfest (for half the price of the Comet). It gets into places shorter antennas just can't. I highly recommend anyone with an HT to grab one of this type for there EDC bag. They fold over into a U shape and store very easily.
Link Posted: 8/14/2007 1:39:28 PM EDT
Glad to hear you were able to get it worked out!

I would highly recommend that you get stationary antennas for your home. Just hook them to your HT with SMA to BNC or whatever adapter. You can get by with much less power and they are a whole lot more durable. I've been using the Arrow solid aluminum J-Pole with great success. I picked up another today to keep in my vehicle emergency kit :) www.arrowantennas.com I know I've been plugging Arrow a lot but I cannot say enough about Al and his antennas. I'm putting together an emergency communications plan for a local organization that will cover thousands or square miles and plan to equip everyone with a Arrow J-Pole.
Link Posted: 8/14/2007 9:43:47 PM EDT

Originally Posted By GlockTiger:
Now since my original issue is solved, I'll hijack my own post -- I have concluded that my Comet SMA-503 STINKS.
www.gigaparts.com/parts/gpcpa/original/zcm-sma-503.jpg
It truly performs worse than the stock duck on both my VX-6 and VX-2.


Mine works a HECK of a lot better than the stock VX-2R ducky. However, I've noticed that the VX-2R's SMA connector occasionally makes poor contact with whatever antenna is attached to it. Judging by the reviews on eham, this is apparently a common problem on VX-2Rs. After I removed the rubber water plug from the SMA connector (thereby allowing the antenna to seat further on the connector), the problem seemed to go away.

Perhaps this is what you've been experiencing with the Comet?
Link Posted: 8/15/2007 7:20:15 AM EDT

Originally Posted By Skibane:
Mine works a HECK of a lot better than the stock VX-2R ducky. However, I've noticed that the VX-2R's SMA connector occasionally makes poor contact with whatever antenna is attached to it. Judging by the reviews on eham, this is apparently a common problem on VX-2Rs. After I removed the rubber water plug from the SMA connector (thereby allowing the antenna to seat further on the connector), the problem seemed to go away.
Perhaps this is what you've been experiencing with the Comet?


Good point about the contact. I heard of that happening but haven't checked recently.


The Preparded:
I would highly recommend that you get stationary antennas for your home.

Yep, got a GP-3 on a mast outside.

The HT's aren't my base rig anyway -- just doing some range experiments with my buddy 2mi away.
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