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GMRS 2nd harmonic interference to 900Mhz Phone

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swen_out_west

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So I have been taking an older gentleman/neighbor around to his appts after hip surgery and stopped near his house (60 yards away) to check a message he had left for me before I headed to town. I was talking on GMRS 5/ CC 19 and complaining how his old cordless phone is so hard to understand with my hard hearing through all of the static and the TV being loud in the background.

Turns out about 10 minutes later he left another message reminding me about picking him up at 7:30 AM. He ended the message with BTW, I heard everything you were saying through my 'crappy old cordless phone' and I turned down the TV volume.

Yes, I did the math 462.650 x 2 falls right in the 902-928 MHz range of the old 900 Mhz FM phones.

I guess my post has one of 2 points.

1. Radio traffic can be overheard even by people not on that particular frequency/band. So the old adage of watch what you say even when you think someone isn't listening applies.

2. I was right about his old crappy cordless phone. Even though I am sure he is going to point the finger at it being my problem even though this is a brand new Midland MXT 115 and I am legally complying with all FCC Part 95 regulations.

So the question is: other than not transmitting when I am that close to his house is there any way to minimize this. Some of you may know my past problems of finding a clear channel void of interference from illegal FRS repeaters around here so changing the frequency is not an option. I could ask him to change the channel on his phone (if it's an option), but knowing him, I doubt he will, just say how it's all on me.

I guess my biggest question is that he also is a big stickler for rules and regs, (he's proud of how many CB'rs he turned in to the FCC 'back in the day', causing even the slightest interference to TV's and Radios), is there any fallout on my end? The caveat of that is, if there is any past history of complaints they'll just chalk it up as him whining yet again.

I am actually surprised he even heard me since I don't even start using that channel until I head to town around 7:45 and he is usually to bed by 7pm.

I guess the only thing I can do is apologize and say I'll not transmit when I am that close to his house and try to downplay the conversation saying something like 'well, it explains why your old phone has so much static if it's not properly filtering my 2nd harmonic'. Besides if he complains too much he can always find another friend or relative to take him around and take care of his dog, (wait he doesn't have anybody else but me).
 
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RFI-EMI-GUY

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Buy him a new DECT cordless phone.

I had a co worker who had an older Panasonic spread spectrum cordless phone. The base unit operated on 2.4 GHZ while the handset was 900 MHZ. Anyway he was complaining about the range getting poor so I offered to take a look. 1) the 2.4 GHZ power amplifier was smoked. 2) while researching the schematic (from FCC OET website) I discovered that while the radios were indeed spread spectrum, the spreading and despreading was done at 2.4 GHZ and 900 MHZ respectively, but required an analog FM IF in the 460 MHz. You could hear the conversations clearly on a nearby scanner. I told him to replace them rather than fix.

Sent from my SM-T350 using Tapatalk
 

swen_out_west

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That's a great idea. Just checked Newegg,com and I can get one with an answering machine like his for $30. A lot, cheaper and easier in the long run than me changing what I have.

I'll just have to sell him on the idea of it being a lot clearer and with the frequency spread, a lot less interference from outside sources and more private.

I'll actually show him the actual item description write up.

"DECT 6.0 DIGITAL TECHNOLOGY
Utilizing the latest-available frequency band, this interference-free technology provides superior voice and sound quality, and higher protection against eavesdropping, than 2.4GHz and 5.8GHz phone systems."

When he asks why they don't mention 900 MHz, I'll just mention how with the interference issues of 900Mhz and open FM frequency, that they started to shift away from them years ago.

Now I just need to sell him on how it really isn't anybodies fault other than the system design of the old 900 MHz phones. Maybe by buying him the phone it will show that although there is nothing I can really do about it, I am going out of my way to try to resolve the issue.
 
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swen_out_west

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but required an analog FM IF in the 460 MHz.
So that probably reads 460 range. So he's probably using the same channel as my 2nd harmonic. Which inversely tells me that his IF is the same as my output freq,

So it probably is as simple as him changing the channel on his phone if that's an option. But since he overheard me complaining about how crappy his cordless sounds, I can redeem myself by buying him the latest and greatest phone.

Since the cat is already out of the bag, I'll just say how now with my hard hearing I'll be able to understand him better when he leaves me a voicemail.
 

swen_out_west

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I need to do more tests. I think that my cell phone actually dialed the last number which would have been him and he picked up the conversation inside the truck not the radio. Even though it is totally possible.

The reason why I think it is the cell phone is that he is threatening to call the FCC on me for using the F word and my girlfriend can attest to the fact that this Sailor doesn't cuss on the radio. I really don't know what his problem with radio enthusiasts is. Although he was going to call the police for a bike on the wrong side of the road this morning, so I guess he just has nothing better to do than call the authorities for every violation he sees..

Plus, I think he heard comments that weren't part of the radio conversation, because the tension was pretty high this morning. But considering that he has no friends or family willing to take care of him during rehabilitation, he;s stuck with me.
 

mmckenna

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Out of band emissions on those radios should be really low. FCC requires this as part of the certification process.

If your radio is working outside of specs, it would be your responsibility to address that.

But, it sounds like the issue was more than likely your cell phone. Asking him if his phone rang before he heard you would narrow that down, as would checking your outgoing call logs.
 

RFI-EMI-GUY

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Why are you bothering doing favors for this guy? You need to pick better friends....If he were to threaten me, I would get a restraining order and tell the police he is listening in and repeating private conversations.
 

swen_out_west

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Out of band emissions on those radios should be really low. FCC requires this as part of the certification process.

If your radio is working outside of specs, it would be your responsibility to address that.

But, it sounds like the issue was more than likely your cell phone. Asking him if his phone rang before he heard you would narrow that down, as would checking your outgoing call logs.
No I checked it I after posted that. It was the phone but he just pinged on the radio because he heard my call sign at one point.

I thought so. Sorry to have posted this last night but I was tired and at my wits end with helping this guy for a month.

He should have taken me up on buying a new cordless phone for him when we were at WalMart and I was still trying to figure out what happened.

Now I know why the tension was so high. He most likely overheard the truck conversation which is the truth that probably really hurts. The conversation with my 21 year old daughter was "I am at my wits end dealing with this ------- guy. His own brother lives 5 miles down the road and won't even ------- talk to him. He's got nobody but me, how ----- up is that.'
 
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mmckenna

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Well, kudos for you for helping this guy out when no one else will. The world needs more of that kind of stuff.
If it's an issue, tell him the truth. I'm sure he's as frustrated as you are. Most people don't like having to rely on someone else, especially older males who were at some point able to take care of themselves.

I volunteer with a homeless advocacy/assistance group. It's hard for some of them to accept assistance from others, but they've always been pretty gracious about it. Occasionally some get a little cranky at times, but it's important to remember they've lost a lot.

You are probably a blessing to that guy. He may not say it, but I'm sure he feels it.
 
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