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Repeater overload on summit?


#1

So first activation today(yay!) of W7W/NO-073 ran into a bit of a snag with I think was a nearby repeater(~200ft) and trying to understand it more for future activations.

Since Blue Mountain is pretty far off the beaten path in the Olympic National Park this looked to be a solar powered only repeater w/ 2 small 1’x2’ panels. Looking up the repeater afterwards confirmed that it’s a part of ~5 other repeaters on 168mhz with same input/output frequencies and different PL tones at each site.

Anyway, I was using my VX8-DR on 146.520 with a 15" whip antenna hoping to get a little bit of extra gain. When a S2S came up it appeared that the repeater would stomp on the other signal with a full S9 signal but zero actual audio in the FM modulation. It seems like I could position my body around the antenna to interrupt it but didn’t seem pretty consistent.

After that contact I switched over to my usual, 5" whip antenna and didn’t appear to have any more issues but I couldn’t tell if that was because the repeater wasn’t active or I was using a less sensitive antenna.

So, was that RF frontend overload or something else? I’ve been a little surprised with some of the issues I’ve seen on the VX8(if both channels are active, sequelch sometimes breaks second channel and scanning that switches between 2m/70cm causes audio issues when the other channel opens squelch) so I’m trying to figure out if it’s a common issue with the VX8 or just summit conditions.


#2

Happens with my Yaesu Vx-8g when in the proximity of tons of RF such as repeaters, utility or whatever.

There is a Attennuation menu item (number 1 on mine and page 130 in manual) that you should turn on which generally solved it for me.

Paul


#3

The VX8 is well known for being rubbish in this respect. It’s the same as many super swish fancy handheld radios. There are radios that work is such environments, there has been discussion on here in the past, the search facility will help you find them.

From personal experiance and personal reccomendation, the following work.
Yaesu VX-170 (and all other family members)
Yaesu FT-270 (and familiy members)
Yaesu FT-60
Yaesu FT-290 (multimode)
Kenwood TH-79 (old dual bander)
Yaesu FT-70 (modern dual bander with C4FM digital)
FT-817 (multimode)

There will be others, but those above do work. I have owned plenty (and still do) that are unusable at such sites.


#4

That’s a real shame, I’m reading elsewhere that since it has pretty wideband RX that makes it more susceptible to these types of things.

It (was) one of Yaesu’s few waterproof radios, I’m going to guess the VX-6 has the same problems too. It’s a shame since I really like having two receive channels on a HT but may have to look into something with a more robust front end for activating.


#5

Good call on ATT, I know I had it on my KX3 but didn’t realize it was an option on the VX8. I’ll give it a shot next time I see it happening although it’s a shame to knock off 10db.


#6

Ive been happy with my VX-8 and typically use a role up J pole hanging from a telescopic mast which really makes it shine compared to a rubber ducky.

Certainly a better solution than the 2m module for the KX3 which I also have and is at best rated “OK”.


#7

Nice part of the world and I did some activation near your peak 2 years ago.

Darryl, WW7D the W7W AM is a big VHF+ operator and should be able to point you to peaks that are VHF friendly in your part of the world.

Paul


#8

An alternative is to insert a low pass filter (because most of the higher power stuff is above 148) into the antenna circuit, ie. a small box containing a filter is connected to the HT and the antenna is connected to the filter. This will sacrifice a few db of sensitivity but knock down the big local signals by much more.

Might need to build it yourself though, not usually available at the local store.

73 Andrew VK1DA/VK2UH


#9

I’m guessing such a filter can be of the “Coax-Stub” kind which we used to use to stop 2m AM Amateur transmitters interfering with wide-open TV receivers.

Ed.


#10

Coax stubs are the obvious choice but they dont have the Q need Ed. That was were I started thinking. When I get back (sat in Prague Airport now) I’ll post a link to a damn fine filter that does what we need but does involve a little bit of metal work. It can be left in the transmit side.


#11

It’s front end overload/de-sense.

You need a narrow band pass filter. Something like

http://www.sv1bds.gr/homebrew/filters/33-2m-band-pass-filter
lots of other designs around if you google “2m band pass filter”

Colin


#12

Hi Val,

The VX8 is renown for being rubbish at handling ‘out-of-band-signals’. However outwith this limitation, it is pretty sensitive, and certainly good at pulling in distant signals.

Now as mentioned, further down the thread, in my case I have two BP filters. Both are modified commercial filters. One has ~ 0.5db insertion with limited band pass characteristics (good for SOTA sites that are not shared with on-site transmitters) and the other has a 6dB insertion but is tight as a ‘badgers derrière’ and nothing gets through it other than 2 metres. As you would expect both are compact. The 6dB is 100 x 60 x 30mm and the 0.5 is slightly bigger.

I mainly use these filters in England (G) where there is a lot of communal sites that are SOTA Summits.

73

Jack(;>J


#13

Great call on the filter, I’ve already got a BNC adapter to make antenna swapping easier so adding something like that might not be too hard. That’s definitely my preference over an attenuator.


#14

Oh yeah, it’s a wonderful place, we just moved to the area a few months ago(my wife grew up here) so really looking forward to getting out and exploring the area.

There’s a very healthy VHF activiation community out here and almost all the mountains face into PA/Victoria so chances of a failed VHF activiation seem pretty low.

I’ve got a KX3 as well but haven’t gone through the effort to get a portable antenna setup put together yet(although it’s on the list).


#15

Ed, as promised, there is an article for exactly the kind of notch filter needed to remove the typical interference source in the June 1997 issue of CQ VHF magazine “Build a 2m intermod Notch Trap”. Here’s a link to it: http://www.n5dux.com/ham/files/pdf/Build%20a%202m%20Intermod%20Notch%20Trap.pdf


#16

Welcome to the Pacific Northwest!!

Preferred HF antenna by many in NA is the End Fed and LNR’s Trail Friendly 10/20/40m works like a champ for me (and many others).


#17

What about something like this? https://www.hobbypcb.com/products/uhf-vhf-radio/144mhz-band-pass-filter


#18

Probably not. What’s the rejection at 150-160MHz? That’s where the interference is. You need a really steep notch. Something with a very high Q.


#19

I have a VX-6 and I activated in July just prior to you. I do not re-call any issue because of a repeater or anything. I am pretty sure I used a J-pole and likely switched to a telescopic whip (RH-205) to start and finish. The VX-6 has an “antennuator” that can be used in these situations, but again, I do not re-call any issues when was there…


#20

There appears to be no rejection near the ham band from that filter.

How do you know the interference is in that band? Seems like you’d need to take a spectrum analyzer up to see where the energy is, unless I’ve missed something.