Yaesu: VX-7R HT - Understanding RX for the NOAA weather freqs?

[zuren]

I recently picked up a Tera TR-590 HT and have been playing with it side-by-side with my Yaesu VX-7R. One thing I'm noticing is that the RX on the NOAA weather (WX) frequencies is MUCH better on the TERA. The Tera has the factory rubber duck antenna, and I have the factory rubber duck and a telescoping Smiley antenna for the Yaesu. It doesn't matter which antenna I have on the Yaesu - the Tera is pulling in a perfectly acceptable signal while the Yaesu sits silent. If I press the "monitor" button on the Yaesu, I can hear a bit of something, but it is pretty bad.

From what I know, the Yaesu has the weather frequencies built into the firmware of the radio and there is nothing that I see that I can tweak in the VX-7 Commander software; I haven't tried CHIRP yet. I have tried adjusting the RX Mode via the keypad for the weather channels (from NFM to WFM) and that helps, but as soon as I change to a different frequency, the radio changes my edit back to NFM.

So I'm trying to understand why a "CCR" is outperforming my $300+ HT on the WX receive, especially a radio that has a dedicated WX memory bank like the VX-7R. Frequencies of 161.xxx to 163.xxx lay right in the middle of the HAM bands, and I have a better antenna for the Yaesu, so this is not what I would expect. I'm guessing I may have changed a setting somewhere but I'm not sure what, and was hoping to get some ideas from the community here.

Thanks!

 

[zuren]

Frequencies of 161.xxx to 163.xxx lay right in the middle of the HAM bands...

Edit - This statement is not entirely accurate, but the published receive range for the VX-7R by Yaesu is 137-174 MHz...so it falls in the middle of that range.

 

[AK9R]

Here's a quote from the Specifications page in the Yaesu VX-7R Operating Manual:

Specifications are subject to change without notice, and are guaranteed within the 50/144/222/430 MHz amateur bands only.

Yaesu is providing coverage outside the amateur radio bands as a bonus feature, but the radio is designed to be an amateur radio transceiver so the performance is optimized for the amateur radio bands. This is pretty typical of amateur radio gear that can receive outside the amateur radio bands.

Also, don't discount the antenna as a variable in your test. If you are going to make a receiver sensitivity judgement, you should make sure you are comparing apples to apples.

 

[zuren]

Here's a quote from the Specifications page in the Yaesu VX-7R Operating Manual:



Yaesu is providing coverage outside the amateur radio bands as a bonus feature, but the radio is designed to be an amateur radio transceiver so the performance is optimized for the amateur radio bands. This is pretty typical of amateur radio gear that can receive outside the amateur radio bands.

Also, don't discount the antenna as a variable in your test. If you are going to make a receiver sensitivity judgement, you should make sure you are comparing apples to apples.

I ordered a BNC adapter for the Tera, so I can do a true side-by-side, apples-to-apples comparison with the telescopic antenna.

Understood about what the radio was designed for, and what it "might" be able to do. Would having an antenna more closely tuned to the WX freqs. (like one of these tuned to 160 or 165 MHz - Commercial) help my performance?

Thanks!

 

[KE5MC]

...snip...

Would having an antenna more closely tuned to the WX freqs. (like one of these tuned to 160 or 165 MHz - Commercial) help my performance?

Thanks!

Receive only operations don't see the same benefit from a tuned antenna as a transceiver would. Not to say there is no performance increase, but usually not readily apparent.

Have you tried all the programmed weather channels on the radio? Not uncommon to hear more than one, but typically only one is received with good signal strength.

Mike

P.S. I have an iCom ID-51 toped with an BNC adaptor to allow me to change antennas easily. A short stubby about 3 inches tall. Then a 9 inch and 13 inch all three are 'tuned' dual band antennas. Antenna length will help to capture more signal, but even on the stubby my HT easily receives the local weather channel. I wondering if your antenna connector on the Yaesu is at issue here. Are you able to talk thru repeaters close to you?

 

[KE5MC]

Cancel what I said in my last post!

"I have tried adjusting the RX Mode via the keypad for the weather channels (from NFM to WFM) and that helps."

That registered but on the way to lunch I realized that's backwards. It should not sound better meaning louder/stronger in this case on WFM. I betting you have a bad crystal filter in the NFM path.

I found the following about crystal filters.

Yaesu VX-series sensitivity issue repair

Mike

 

[zuren]

Cancel what I said in my last post!

"I have tried adjusting the RX Mode via the keypad for the weather channels (from NFM to WFM) and that helps."

That registered but on the way to lunch I realized that's backwards. It should not sound better meaning louder/stronger in this case on WFM. I betting you have a bad crystal filter in the NFM path.

I found the following about crystal filters.

Yaesu VX-series sensitivity issue repair

Mike

So switching the RX Mode to WFM for the WX channel takes it from being deaf to at least opening the squelch. The RX is pretty bad but at least you here something.

After reading the link you provided and searching a bit more on the part number that lead me to other links, I think I'm beginning to agree that maybe the filter is bad. I was playing with the squelch settings a few weeks ago because I didn't think something was right, but I chalked it up to my lack of knowledge. It has been babied all its life (mostly lives in a padded Pelican case) but it is a 2007/08 vintage radio and if this is a known design flaw, then maybe all I did is delay its demise.

 

[KE5MC]

Likely you have researched the issues more than I have. My Kenwood D710 has a similar issue with crystal filters and the DC coupling into the filter was said to cause the filter failure.

Might be a design issue for the VX-7, but not sure. If it is maybe Yaesu may have a repair plan on the 'down low' for this issue. I would certainly contact them to see what they say. Also the repair cost might be reusable as that's not an inexpensive radio. I had a VX-6 then jumped to VX-8. Both nice radios.

Good Luck!
Mike

 

[ko6jw_2]

According to Yaesu the VX7 has a sensitivity of .2microvolts for a 12db SINAD from 150-174Mhz. This should result in very good reception of NOAA stations. I have a VX6 which does very well in that range. There may be something wrong with the radio. Maybe you can find a ham with a service monitor to check the sensitivity. How does it perform on 2 meters?

 

[zuren]

Update:

So I watched these videos that gave me an idea of how to diagnose the radio and what I'm up against, even though it is a VX-6R:

https://www.youtube.com/watch?v=MFyehZ2hg1I

https://www.youtube.com/watch?v=6s8eWVPTdhQ&t=53s

I took my volt meter and measured across the contacts shown in the videos, and it appears that the filter is bad so I will be ordering a new one.

Is there a recommended width of solder wick for this kind of work? The contacts on this HT are pretty tiny.

Thanks!

 

[prcguy]

I had a VX-7 for many years and it received NOAA weather as good as any other hand held receive I've owned. Sounds like you've ruled out antennas and other things so in my opinion I think its time to bench test the VX7 for sensitivity in both the amateur bands and NOAA. It could be broken.
prcguy

 

[TailGator911]

What prcguy said. I own a VX-7R and use it primarily for SkyWarn but I have several freqs in there for on the road - NOAA weather, local repeaters and local conventional freqs that still broadcast some of the OHIO MARCS-IP dispatch and tones on the 154.400mhz frequency, among others, and the VX-7R is loud and clear on most all local (and weather) channels I have programmed. Best little quad-band HT I have ever owned.

JD
kf4anc

 

[KE5MC]

Update:

...snip...

Is there a recommended width of solder wick for this kind of work? The contacts on this HT are pretty tiny.

Thanks!

I have some American Beauty 'Dri-wik' that's .050" wide the smallest I have. Small is good as you don't want the width of the wick to bridge to other contacts. Without seeing what you have to replace I would try that size. Surface mount can be tricky. For removal of a known bad part I would consider a small nozzle heat gun to remove the part and the wick for cleanup. Then figure a way to hold the part in place while soldering each contact point.

Good Luck,
Mike

 

[zuren]

Just wanted to close this thread out. I received all of the parts and tools required to change the filters and did the repair last night. Receiving the NOAA WX frequencies has been restored!

I'll continue to test but everything seems to be working as it should! A few notes:

- Slotted nuts around the selector knob stem and the programming/headphone port required a "camera spanner wrench". I probably could have fussed around with a screwdriver, but the space was tight and I didn't want to damage anything. I bought a pair with the curved tips and it worked great - https://www.google.com/search?q=cam...jKbaAhVR2FMKHdRyCSQQ_AUICygC&biw=1119&bih=423.

- Removing the old solder was MUCH harder than putting the new solder on.

- I replaced both filters (same part) when I was in there. I figured if one failed, the other could sometime soon as well. For $0.61, it was worth my time while I had it apart to just replace both.

Here is all of the information I gathered to do this work:

https://forums.radioreference.com/amateur-radio-equipment/360118-yaesu-vx-6r-problem.html

Yaesu VX-series sensitivity issue repair

Yaesu VX-6R Receive Fix - Chris's Stuff

VK4ION Resources

Benjamin Koe: YAESU VX-6R Ceramic Filter Replacement

Filter R&R
Part 1 - https://www.youtube.com/watch?v=MFyehZ2hg1I
Part 2 - https://www.youtube.com/watch?v=6s8eWVPTdhQ
Desoldering - https://www.youtube.com/watch?v=Z38WsZFmq8E
General searches for "Through-hole soldering"

Parts/Tools
- Filter H3900531, now superceded by H3900572A - ~$5 for 3 filters including S/H direct from Yaesu
- Kester 44 solder
- Amtech 559 flux
- Camera spanner wrench
- also bought a new soldering kit and a "helping hands" unit with a magnifying glass since my existing soldering iron was too big with no temp control, and there was no way I was going to be able to see the tiny contacts I was working on with my eyes.

Service manual
http://www.repeater-builder.com/yvs/pdfs/yaesu-vx-7r-technical-supplement.pdf

I hope this helps someone in the future!

 

[KE5MC]

Zuren,
Excellent job, working at the component level is something I can do. It’s getting to that point with all the PCB layers and ribbon connections that puts me off on the small electronics.
1st rate Google-fu too
Mike

 

[wyShack]

Another item to think about is the antenna. An antenna optimized for the two meter ham band, especially one with gain is going to have a narrow bandwidth. This would have the effect of reducing sensitivity on receive when out of the 2 meter band.

Any 'rubber duckie' style antenna is going to be a compromise at best-we use them on handheld for their durability and convenience -not performance or bandwidth.