Frequency jump? My radio or just overpowered transmitter?

[TrikeRadio]

NOTE: I don't know if "Frequency jumping" is the right term but i am just trying to describe what i have heard so forgive my noob description.

What I experienced:

1. I am using a little Tidradio TD-H3 with a mobile mag-mount antenna on a metal cookie sheet as a makeshift "base" station and checking in to a Simplex Net event.
2. Everyone involved in the net was using no ctcss tones on ch 20 (462.675)
3. However I kept getting a high powered station that was for sure on 462.700 (and on a high power repeater in the area) break through while I was on 462.675
4. I had the TD-H3 in duel watch mode but had both on the same channel 20 (462.675) and I found that if I switched from A to B or B to A when the 700 station broke through the radio would go back to the 675 stations and "squelch" out the one that broke through from the 700 frequency. (I discovered that this worked but was not sure why)

So, my three QUESTIONS:

1. Was the breaking through to my monitoring radio on 675 from the strong 700 transmission purely because of the power of the transmitting 700 station/repeater and this would happen with any radio?
2. Was it just because my little cheapo TD-H3 can't handle the situation properly and is either a bug or result of being a cheap radio?
3. Why does it seem to cut out the interfering 700 station when I switch the A/B channel selector and work until the next start of a subsequent transmission that again breaks through into my monitoring of 675?

Any answers, Input, speculation, similar experiences of this same situation, or questions to me about something I forgot to specify in this post.... all welome. Just trying to figure out why this happened.
 

Thank you.
 

[WRXL702]

Lower End $$ GMRS Transceivers Do Not Have The Front End Receiver Filtering As Do Commercial Grade Radio Receivers. Therefore, If In Close Proximity Of A 50 Watt Base Station With A High Gain Antenna - You Most Likely Can & Will Hear That Transmission Not On Your Selected Channel / Frequency.

Lower End $$ Radios Work Fine When Not Close To Adjacent Channel Transmitters, But They Do Not Have The Selectivity / Sensitivity Available On A Commercial Grade Radio. This Most Likely Will Be A Common Occurrence Especially When The Frequencies Are So Close In MHz. Spacing (462.675 / 462.700.) 

The Only Major $$ Difference In Radio Types, Other Than Some Special Functions - Is The Receiver Front End Filtering.

[SteveShannon]

31 minutes ago, TrikeRadio said:

NOTE: I don't know if "Frequency jumping" is the right term but i am just trying to describe what i have heard so forgive my noob description.

What I experienced:

1. I am using a little Tidradio TD-H3 with a mobile mag-mount antenna on a metal cookie sheet as a makeshift "base" station and checking in to a Simplex Net event.
2. Everyone involved in the net was using no ctcss tones on ch 20 (462.675)
3. However I kept getting a high powered station that was for sure on 462.700 (and on a high power repeater in the area) break through while I was on 462.675
4. I had the TD-H3 in duel watch mode but had both on the same channel 20 (462.700) and I found that if I switched from A to B or B to A when the 700 station broke through the radio would go back to the 675 stations and "squelch" out the one that broke through from the 700 frequency. (I discovered that this worked but was not sure why)

So, my three QUESTIONS:

1. Was the breaking through to my monitoring radio on 675 from the strong 700 transmission purely because of the power of the transmitting 700 station/repeater and this would happen with any radio?
2. Was it just because my little cheapo TD-H3 can't handle the situation properly and is either a bug or result of being a cheap radio?
3. Why does it seem to cut out the interfering 700 station when I switch the A/B channel selector and work until the next start of a subsequent transmission that again breaks through into my monitoring of 675?

Any answers, Input, speculation, similar experiences of this same situation, or questions to me about something I forgot to specify in this post.... all welome. Just trying to figure out why this happened.
 

Thank you.
 

Do you have a typo in bullet point #4 where it says “had both on the same channel 20 (462.700)?”

[TrikeRadio]

4 minutes ago, SteveShannon said:

Do you have a typo in bullet point #4 where it says “had both on the same channel 20 (462.700)?”

oh.. yes. thanks... typo... should have said 20 (462.675)

[TrikeRadio]

8 minutes ago, WRXL702 said:

Lower End $$ GMRS Transceivers Do Not Have The Front End Receiver Filtering As Do Commercial Grade Radio Receivers. Therefore, If In Close Proximity Of A 50 Watt Base Station With A High Gain Antenna - You Most Likely Can & Will Hear That Transmission Not On Your Selected Channel / Frequency.

Lower End $$ Radios Work Fine When Not Close To Adjacent Channel Transmitters, But They Do Not Have The Selectivity / Sensitivity Available On A Commercial Grade Radio. This Most Likely Will Be A Common Occurrence Especially When The Frequencies Are So Close In MHz. Spacing (462.675 / 462.700.) 

The Only Major $$ Difference In Radio Types, Other Than Some Special Functions - Is The Receiver Front End Filtering.

Thanks.. Yeah I suspected that it was just the low cost radio that was the cause of it. So, If I get a better mobile unit in the future, I should not experience this I guess.

It was a rare occurrence and I was glad I could do the a/b switch to cut out the interference as it occurred... but yeah not ideal that is for sure.

[SteveShannon]

2 minutes ago, TrikeRadio said:

oh.. yes. thanks... typo... should have said 20 (462.675)

On dual watch your radio might be scanning quickly between A and B. If 462.675 is quiet when the radio goes to the other side and there’s a strong signal on 462.700 at the time your tuner could capture the strong signal. There’s very little spacing between them. Try turning off dual watch, especially when both are on the same center frequency. 

[TrikeRadio]

14 minutes ago, SteveShannon said:

On dual watch your radio might be scanning quickly between A and B. If 462.675 is quiet when the radio goes to the other side and there’s a strong signal on 462.700 at the time your tuner could capture the strong signal. There’s very little spacing between them. Try turning off dual watch, especially when both are on the same center frequency. 

I did try turning off duel watch, but it was still happening.

With duel watch off I could not switch to cut out the interfering transmission. I would only hear the 700 signal until they stopped transmitting. So, I left it on duel watch and just kept switching to cut out the 700 signal when it happened. Not ideal, but it "worked".

[SteveShannon]

5 minutes ago, TrikeRadio said:

I did try turning off duel watch, but it was still happening.

With duel watch off I could not switch to cut out the interfering transmission. I would only hear the 700 signal until they stopped transmitting. So, I left it on duel watch and just kept switching to cut out the 700 signal when it happened. Not ideal, but it "worked".

It might be your radio, but it might also be the radio transmitting on 462.700. Perhaps it’s slightly off frequency or transmitting wider than it should. 
I don’t know if setting your radio to narrow on 462.675 would help but I would be curious. 

[TrikeRadio]

58 minutes ago, SteveShannon said:

It might be your radio, but it might also be the radio transmitting on 462.700. Perhaps it’s slightly off frequency or transmitting wider than it should. 
I don’t know if setting your radio to narrow on 462.675 would help but I would be curious. 

Could also be the radio is confused because I was listening on 675 in OPEN, maybe somehow that is a part of allowing the blead-over too?

as WRXL702 said...

1 hour ago, WRXL702 said:

Lower End $$ GMRS Transceivers Do Not Have The Front End Receiver Filtering As Do Commercial Grade Radio Receivers. Therefore, If In Close Proximity Of A 50 Watt Base Station With A High Gain Antenna - You Most Likely Can & Will Hear That Transmission Not On Your Selected Channel / Frequency.

Could be the radio just does not do filtering front end because it is a cheap radio.


When I am using CTCSS or DCS tones I don't seem to see that bleed over, but if two repeaters are on the same frequency with different tones, sometimes I hear the more powerful signal (with a dfferent tone) break in after the one with the correct tone opens the squelch.

 

[Socalgmrs]

3 minutes ago, TrikeRadio said:

Could also be the radio is confused because I was listening on 675 in OPEN, maybe somehow that is a part of allowing the blead-over too?

as WRXL702 said...

Could be the radio just does not do filtering front end because it is a cheap radio.


When I am using CTCSS or DCS tones I don't seem to see that bleed over, but if two repeaters are on the same frequency with different tones, sometimes I hear the more powerful signal (with a dfferent tone) break in after the one with the correct tone opens the squelch.

 

This is because the squelch is still open from the previous key up with the correct tones.   The tone I my opens the door.   Nice it’s open it’s free game what signal gets in strongest.  

[TrikeRadio]

15 minutes ago, Socalgmrs said:

This is because the squelch is still open from the previous key up with the correct tones.   The tone I my opens the door.   Nice it’s open it’s free game what signal gets in strongest.  

Even if they are on 462.700 and I am monitoring 462.675? Just the signal strength and the squelch opened by the other transmission on 675?
Will that even happen one higher quality / more expensive radios?

[SteveShannon]

46 minutes ago, TrikeRadio said:

Could also be the radio is confused because I was listening on 675 in OPEN, maybe somehow that is a part of allowing the blead-over too?

Not really; the front end (RF) of the radio is on the outside of the tone squelch. That’s where the strongest signal is captured.
Being open squelch allows your radio to audibly reproduce whatever the RF stage hears, but does nothing to prevent the RF stage from detecting it.

The interference from the stronger signal happens in the RF stage before it ever gets to the squelch. 
 

[amaff]

2 hours ago, SteveShannon said:

It might be your radio, but it might also be the radio transmitting on 462.700. Perhaps it’s slightly off frequency or transmitting wider than it should. 
I don’t know if setting your radio to narrow on 462.675 would help but I would be curious. 

Yeah, probably a little of column A (it's a $35 radio), and a little of column B (slightly off frequency in your direction, and / or more bandwidth than it should use).
It would be interesting to see if a radio with a more selective filter had the same issue.

[dosw]

It's possible your radio was being overloaded by a strong signal. But it's also possible someone was messing around and retransmitting on the second frequency. The other day I was hearing fire/medical dispatch on GMRS channel 1. It was covering a broad area, at least ten miles, as I was driving around. And I was hearing it on an RA87, UV-5G Plus, and GXT1000. The only conclusion I could come up with was that someone with a lot of antenna, or too much power, was rebroadcasting the dispatch frequency onto 462.5625 for awhile. Later in the day it was gone, and I haven't heard it since.

[AdmiralCochrane]

18 minutes ago, dosw said:

It's possible your radio was being overloaded by a strong signal. But it's also possible someone was messing around and retransmitting on the second frequency. The other day I was hearing fire/medical dispatch on GMRS channel 1. It was covering a broad area, at least ten miles, as I was driving around. And I was hearing it on an RA87, UV-5G Plus, and GXT1000. The only conclusion I could come up with was that someone with a lot of antenna, or too much power, was rebroadcasting the dispatch frequency onto 462.5625 for awhile. Later in the day it was gone, and I haven't heard it since.

I had the same experience with a fairly expensive radio with pretty good filtering.  I was only 200 - 300 feet from a local dispatch repeater.  Apparently first harmonic of their UHF frequency was right in GMRS.

[dosw]

1 hour ago, AdmiralCochrane said:

I had the same experience with a fairly expensive radio with pretty good filtering.  I was only 200 - 300 feet from a local dispatch repeater.  Apparently first harmonic of their UHF frequency was right in GMRS.

In my case I heard it from home, heard it from the freeway entrance, heard it as I left the salt lake valley, passing beyond line of sight to the valley. Ten mile radius from the freeway entrance. And only that one day. It has to be someone messing around.

It was a week or so after repeater linking bit the dust, so it might have been an act of protest in some way