2m Skip?

So I'm monitoring my local repeaters with my BooFunky HT, and I'm in the bedroom.... Folding clothes! The radio is on the dresser (next to the bail money) and it stops scanning in 147.220.

147.220 is a repeater for the Pearland Radio Club, and its about 12 miles from me, but all of a sudden I'm hearing fire tones. Deer Park Pd was dispatching the FD to an unconscious person.

Now the repeater is 12mi from me, but the Deer Park PD is only like 2.

I've NEVER heard DP police dispatch on ANY frequency, and I was pretty sure they were on an 800mhz system.

Is this just a fluke thing based on the location of my radio, the weather, and the proximity of the transmitting station? I wouldn't think they would be using frequencies so close to amateur bands...

Not skip, tropospheric ducting. It happens a lot in the late summer. Sometimes I hear repeaters from way up north down here in San Diego and SoCal hams QSO with hams in Hawaii on 2m.

But it's only one way right? I I transmitted on that frequency from that exact spot in my home, considering I can even get out, would they hear me? Or is that an undeterminable situation?

They might and they might not, hard to know for sure but you're probably hearing a high-wattage repeater from somewhere so it's not likely they'd hear you unless you have a fairly powerful transmitter and high-gain antenna yourself.

OK, two possibilities:
1) Somebody on 147.220 was jerking around.
2) Since the receiver was in scan mode it moved on to the VHF Part 90 band just above 2M and received a regional simulcast frequency. Often a police or fire department also dispatches ambulances that may or may not be a fire rescue unit. In any case the PD always responds to any and all emergencies so they also could have dispatched a PD unit you mistook for FD.
154.79250 KKT848 DP PD Dispatch (simulcast from trunked system)
154.22000 KBG773 103.5 PL DP Fire Dispatch (simulcast from trunked system)
In any case what you heard wasn't DX by any stretch of the imagination, it was a "local" transmission from the Houston suburb you live in. I have no idea how these simulcast frequencies work so I can't say whether they could hear you on that frequency or not. One thing's for sure, they could if you had their talk group and NAC programmed into a Motorola Type II Smartset trunking radio. (;->)

I was in channel scan, not VFO scan.


And I know how they work, we patch in a VHF frequency for our volunteers who only have pagers and no radios. That wasn't what this was. This was a transmission on an amateur band.

baofengs have shit receivers in them. if I am on 440 with mine and a APD officer keys up somewhat close to me I can hear them (they use a 453 rpt out/458 in) if i get close to the apd tower I can hear it all.

so hearing a fd call from a station 2 miles away on vhf with a baocrap isnt "skip" its intermod due to crappy radio.

2m "skip" would be hearing a repeater on 147.22 from a couple hundred miles away.

I have to agree on the intermod theory.

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Originally Posted by K7SGJ

I have to agree on the intermod theory.

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After actually reading your post (like I should have before answering), I would concur with this.

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Originally Posted by W2IBC

baofengs have shit receivers in them. if I am on 440 with mine and a APD officer keys up somewhat close to me I can hear them (they use a 453 rpt out/458 in) if i get close to the apd tower I can hear it all.

so hearing a fd call from a station 2 miles away on vhf with a baocrap isnt "skip" its intermod due to crappy radio.

2m "skip" would be hearing a repeater on 147.22 from a couple hundred miles away.

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Interesting... I must have lucked out with the Baofeng I received then. Standing at a transmitter site, less than 20 ft from an antenna array, nary a bit of intermod.

I have an alternative theory: Was your B VFO on the actual fire frequency, while you were scanning, with dual-watch enabled, but VFO-A locked in for xmit? Which would make it so the scanning stops when something comes in on VFO B, while keeping your xmit VFO on A.

No, I have dual watch disabled. But B was on 443.825, another local radio club repeater.

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Originally Posted by KC2UGV

Interesting... I must have lucked out with the Baofeng I received then. Standing at a transmitter site, less than 20 ft from an antenna array, nary a bit of intermod.
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im sure if you dig a bit, you will find problems.

Mine has great tx audio, another guy in town has one has totally shit tx audio.
rx on these things are as wide open as a barn door.
as for intermod what was the tx site you were standing next to? was you on the same band as it was?
like I said APD here uses 453/458Mhz if one of the cops or I am very close to the tower and I am on 440 Ill hear them. If I am on 2m and get close to another 2m repeater site Ill hear the other 2m repeater

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Originally Posted by W2IBC

im sure if you dig a bit, you will find problems.

Mine has great tx audio, another guy in town has one has totally shit tx audio.
rx on these things are as wide open as a barn door.
as for intermod what was the tx site you were standing next to? was you on the same band as it was?
like I said APD here uses 453/458Mhz if one of the cops or I am very close to the tower and I am on 440 Ill hear them. If I am on 2m and get close to another 2m repeater site Ill hear the other 2m repeater

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I was standing on top of Buffalo's city hall, which is a transmitter site for 3 of the 5 BPD repeater systems (On the UHF band), Buffalo Fire (UHF), and I do believe Buffalo DPW (VHF).

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Originally Posted by KC2UGV

Interesting... I must have lucked out with the Baofeng I received then. Standing at a transmitter site, less than 20 ft from an antenna array, nary a bit of intermod.

I have an alternative theory: Was your B VFO on the actual fire frequency, while you were scanning, with dual-watch enabled, but VFO-A locked in for xmit? Which would make it so the scanning stops when something comes in on VFO B, while keeping your xmit VFO on A.

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I have seven Baofengs and intermod has been an issue on only one of them, the UV-5RA. The rest have been clean.

Yeah, I know. Seven HTs is stupid. I hear that every day at home...

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Originally Posted by W2IBC

im sure if you dig a bit, you will find problems.

Mine has great tx audio, another guy in town has one has totally shit tx audio.
rx on these things are as wide open as a barn door.
as for intermod what was the tx site you were standing next to? was you on the same band as it was?
like I said APD here uses 453/458Mhz if one of the cops or I am very close to the tower and I am on 440 Ill hear them. If I am on 2m and get close to another 2m repeater site Ill hear the other 2m repeater

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Do you have it set on wide or narrow FM?

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Originally Posted by WU9G

I have seven Baofengs and intermod has been an issue on only one of them, the UV-5RA. The rest have been clean.

Yeah, I know. Seven HTs is stupid. I hear that every day at home...

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thats funny... I'm using UV-5RA's...

I always use narrow FM. In fact, although I have a Wouxon, at the hospital (Mom got her new knee yesterday), I fired up the HT...mind you hospitals are full of RF ESPECIALLY their VHF paging systems, and all the EMS repeaters...nary a bit of intermod. and EMS here is on 450 MHz, doctor's pagers on ~153 MHz.

On WFM volume on all but broadcast signals is so low you can't hear it.

I wonder what the first IF of the Baofeng is? If not intermod, this could be an image, too. I can't find any reference to the IF frequency - that would determine the likely 'image' frequency. The intermod rejection is only rated at 60 dB, so that's not miraculously high.

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Originally Posted by K0RGR

I wonder what the first IF of the Baofeng is? If not intermod, this could be an image, too. I can't find any reference to the IF frequency - that would determine the likely 'image' frequency. The intermod rejection is only rated at 60 dB, so that's not miraculously high.

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Good question...

Here's the detailed schematic: http://www.uv3r.com/images/Schematic-Baofeng-UV5R.pdf

Maybe someone can convert that latin into an IF? I can't, beyond my skill level.

Thanks, Cory - my understanding of these little marvels is greatly enhanced!
The radios don't have an IF. They are little software defined radios under the covers! They use the RDA1846 chip, which is a fully self-contained transceiver on a chip. They merely add a microcontroller to run the radio's functions, and receive and transmit amplifiers. The RDA1846 takes the receive input through a pair of mixers with a 90 degree phase shift on one to produce a quadrature output. This is fed into two ADC's, which feed the built in digital signal processor.

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Originally Posted by K0RGR

Thanks, Cory - my understanding of these little marvels is greatly enhanced!
The radios don't have an IF. They are little software defined radios under the covers! They use the RDA1846 chip, which is a fully self-contained transceiver on a chip. They merely add a microcontroller to run the radio's functions, and receive and transmit amplifiers. The RDA1846 takes the receive input through a pair of mixers with a 90 degree phase shift on one to produce a quadrature output. This is fed into two ADC's, which feed the built in digital signal processor.

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Hmmm.... Which makes me wonder: Can you put a Arduino/RaspPi/Parralax in there to turn them into full SDR's?

I concur , Corey. The Baofeng is a SDR. Although I have determined the clock reference as 32.768 KHz. But, there is what looks like a 26MHz xtal connected in series with a 10pFd cap and in parallel with a variable cap and another unspecified cap to ground.... what I did was look at the CPU's specs here.

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Originally Posted by K9CCH

So I'm monitoring my local repeaters with my BooFunky HT, and I'm in the bedroom.... Folding clothes! The radio is on the dresser (next to the bail money) and it stops scanning in 147.220.

147.220 is a repeater for the Pearland Radio Club, and its about 12 miles from me, but all of a sudden I'm hearing fire tones. Deer Park Pd was dispatching the FD to an unconscious person.

Now the repeater is 12mi from me, but the Deer Park PD is only like 2.

I've NEVER heard DP police dispatch on ANY frequency, and I was pretty sure they were on an 800mhz system.

Is this just a fluke thing based on the location of my radio, the weather, and the proximity of the transmitting station? I wouldn't think they would be using frequencies so close to amateur bands...

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I have seen where a corroded antenna clamp can act as a simple mixer. Just add water. When I help maintain the club repeater back home we shared antenna space with a bunch of pager transmitters years ago. There were two pager transmitters that were 600KHZ apart from each other. If it was raining or very humid, When the pager transmitters were transmitting and our repeater would come up, we would get a feed back loop. our output would get cycled back into our input. If not for the delay in the controller the thing would have just howled. Instead it sounded like a cheap CB echo mic on over drive.

The other likely avenue is weak filtering. It's not at all uncommon for cities to use frequencies in VHF high and VHF low bands that duplicate the trunk systems traffic so they can more easily communicate with neighboring services. Sometimes they leave these secondary frequencies running sometimes they don't. This is what you most likely heard. Most trunked systems at very least channel hop and many are digitized like cell phones are. It's unlikely even if you did hear them, that you would be able to make heads of tails out of them. That said, If you put a big enough signal at the antenna, You will get some kind of audio out.

I used to work in the shaddows of a 300ft+ building with a 10KW FM broadcast transmitter on it. We went through about a dozen different radios before we found one that could hear anything besides the one station. We found two the worked. An old KLH desk top radio from the late 60's or early 70's and an old Heathkit AR15 receiver from 72 that my grandfather and I built. Well, OK, he built it and I mostly messed things up for him. What can I say, I was 8 at the time. We could not find a modern receiver that would work.

Archie N8OBM

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Originally Posted by KJ6BSO

Not skip, tropospheric ducting. It happens a lot in the late summer. Sometimes I hear repeaters from way up north down here in San Diego and SoCal hams QSO with hams in Hawaii on 2m.

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A cool tropo-ducting story. Years ago I was talking to friend of mine across town in Ann Arbor on the 145.15 repeater. This machine needs a 100hz PL to open up. After we were talking for a few minutes I noticed the tails were a little slow and the courtesy tone was different when I stopped transmitting. It seemed that I forgot to turn my tone on and My signal was going trough a repeater on the other side of Lake Erie in Cleveland Ohio. That was a good 200+ miles away. Not bad for a 5 watt HT. It also happens pretty regularly in the FM broadcast band. My evil twin brother lives near Cleveland so I visit often. It's not uncommon to hear Detroit FM stations in summer in Cleveland.

Archie N8OBM

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Originally Posted by N8OBM

A cool tropo-ducting story. Years ago I was talking to friend of mine across town in Ann Arbor on the 145.15 repeater. This machine needs a 100hz PL to open up. After we were talking for a few minutes I noticed the tails were a little slow and the courtesy tone was different when I stopped transmitting. It seemed that I forgot to turn my tone on and My signal was going trough a repeater on the other side of Lake Erie in Cleveland Ohio. That was a good 200+ miles away. Not bad for a 5 watt HT. It also happens pretty regularly in the FM broadcast band. My evil twin brother lives near Cleveland so I visit often. It's not uncommon to hear Detroit FM stations in summer in Cleveland.

Archie N8OBM

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They still have radio stations in Detroit? Who gnu?

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Originally Posted by K7SGJ

Who gnu?

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Wildebeest who made that pun please excuse himself?

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Originally Posted by K7SGJ

They still have radio stations in Detroit? Who gnu?

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Even more unbelievable, They have radios in Cleveland!

Archie N8OBM

After noticing the title of this thread, I was reminded of a kid in high school. He stood a little under six feet, and had an animated walk. We nick named him...............well.......you get the idea.

Cleveland?

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Originally Posted by KC2UGV

Hmmm.... Which makes me wonder: Can you put a Arduino/RaspPi/Parralax in there to turn them into full SDR's?

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I kind of looked at that too - it looks to me like the DSP functions are all defined and self contained in the RDA chip. I noticed they have a similar chip - the RDA1847 that appears to have the same functions as the 1846, but it has external analog paths in and out of the chip, too. They say you can use it with an external DSP - which would let you do whatever you want to do I would imagine. I wonder if the 1847 would fit in the UV5R where the 1846 is? You could bring the analog signal out of the box and into an outboard DSP. I've seen efforts to do DSP with the Raspberry Pi.

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Originally Posted by K0RGR

I kind of looked at that too - it looks to me like the DSP functions are all defined and self contained in the RDA chip. I noticed they have a similar chip - the RDA1847 that appears to have the same functions as the 1846, but it has external analog paths in and out of the chip, too. They say you can use it with an external DSP - which would let you do whatever you want to do I would imagine. I wonder if the 1847 would fit in the UV5R where the 1846 is? You could bring the analog signal out of the box and into an outboard DSP. I've seen efforts to do DSP with the Raspberry Pi.

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Looks like someone else already thought of it:
http://hackaday.com/2013/02/28/hacking-a-ham-radio/

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Originally Posted by KC2UGV

Looks like someone else already thought of it:
http://hackaday.com/2013/02/28/hacking-a-ham-radio/

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I never am ceased to be amazed by the creativity of people involved in electronic, communications, or computers. Oh what visionaries. Or hacks.

one hell of a 2m opening last night. picked up repeaters from sw tenn. to VE3 land over to PA

That's when you swing your horizontal beam at them, tune down to the bottom end of the band and toss some CW or SSB CQs at them. That's where the real action is when the band opens.

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Originally Posted by kb2vxa

That's when you swing your horizontal beam at them, tune down to the bottom end of the band and toss some CW or SSB CQs at them. That's where the real action is when the band opens.

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if only I had a beam.... im stuck with a boring ol jpole.