On 7/17/2021 5:19 PM, Don Y wrote:
> On 7/17/2021 6:07 AM, ABLE1 wrote:
>> Hello, I find this VERY interesting. I won't go into the whole story
>> since it is very long but I have a customer that has an alarm system
>> that I installed. It has wireless sensors for doors and such.
>> There has been a few times that the system does not receive signals
>> from the transmitters for periods of time from 45 minutes to 2 days.
>
> 2 *days*? Are you sure someone isn't (illegally) operating
> a transmitter, nearby?
>
That is a possibility. Again finding and proving is the challenge.

>> During this time their garage door opener remote does not work unless
>> you hold it in you hand reach up to within 18" of the opener antenna
>> and then it will work.
>>
>> During that time the problem or source can't be determined.
>> In discussions with neighbors it has be determined that at least
>> 4 others, next door and across the street have experienced the same
>> with there openers.
>>
>> Then it all stops and goes back to normal operation???
>>
>> This happened about 2 years ago and then again about a month ago.
>> That I know about that is.
>>
>> Needless to say when it IS NOT happening it is absolutely impossible
>> to find. When it IS happening it is absolutely impossible to find.
>>
>> The openers have a red LED on the unit that is used for learning in
>> a remote button. Normally it is off until it receives a signal from
>> a remote to open. During these events the LED is solid red for the
>> entire time frame. Then during the end of the event it starts to
>> flicker and then off.
>
> Verify the *complete* behavior of the indicator. Usually, when
> in "learn mode" (activated by a button on the RECEIVER), the
> indicator will flash (until it times out).
>
> Some flash when they detect an obstacle in the path of the door
> (either photoelectrically or by sensing an increased current
> draw by the motor)
>
> Does "lit" coincide with the *entire* open/close cycle? I.e.,
> the behavior you are seeing SHOULD be accompanied by the door
> moving (?)
>
This LED is primary for learning in a remote. And just blinks when the
remote is pushed. Which is seeing the RF Signal. Normally the LED
is off. During my observation at the 45 minute period. The handheld
remote would not work unless it was held up within 18" of the antenna.
Also the Subaru header button did not work. There were two house doors
that would not communicate the doors were open or closed to the security
panel during this time. At the same time the next door neighbor's
garage remote would not work. Then the LED started to blink and then
off. Door contacts then worked as they should. The event was over
and as I am aware has not returned.

>> The security devices are on 319.5 Mhz and the door opener is on 318 Mhz.
>>
>> Is there any thoughts here as to what other than Military Radar that
>> could be causing this issue with such intensity in a small area??
>
> Almost anything can be an "unintentional radiator" -- even things like
> christmas lights!
>
> I'd wonder if someone wasn't (naively) putting a bunch of hash out.
> The "45 minutes" sounds like someone might be "doing something"
> (or USING something) for a short period. The "2 days" suggests it
> got left *on*!
I agree, but when it is not on it can't be found.

> I lived in a house with the garage located beneath the master bedroom.
> Vacuuming the carpet in the MBR would often result in the garage door
> opening. We'd come out, the next morning, to leave for work and
> wonder which of us had "*left* the door open"! (Ans: neither)
>
>> There is a local airport with control tower about 2 miles away.
>
> Possible. Why not go sniffing for signals? TV or radio stations
> nearby?
No Radio or TV nearby. Closest TV station is 6 miles as the crow flies.
But I would think that if something that far away would have a much
broader area effected rather than this very small area of maybe 6 homes.
At least that I know about at this time.

It would make more sense that what ever it is would be located in
one of the nearby houses that is radiating out 306 degrees, but What??
And Where??

>
>> I say a small area (200' square box maybe??) but it could be effecting
>> a larger area but I have no way to know or to find out without having
>> a town meeting.
>>
>> Any thoughts on the subject would be most helpful.
>
> When the problem next manifests, try to shield the affected unit.
> This would at least give you an idea if the interference was radiated
> or conducted. In most places, several homes are fed from a single
> transformer. So, your line is a direct reflection of what's happening
> in your neighbor's homes. Neighbors served by *another* transformer
> will have two transformers acting to attenuate signals between your
> home and theirs.
>
> [Here, it's 4 homes per xformer -- and I can easily deduce which
homes are
> serviced "together" (or service is all below grade)]
This a new 55 and over community that was new in the past 3 years or so.
Houses are rather close and streets are narrow. As things always seem
to go it was first thought that the new security system that I was
installing was the cause of the problem with the Door Opener.........

I have more time in this problem trying to find the source or just
pondering the problem than I want to think about. Total LO$$!!

It is horrible when you can't measure it, see it, touch it, taste it
or even smell it!!!

BTW I may have forgotten to mention that there are two Door Openers in
this house and both react exactly the same way.

From what I gather at this time is that it may be one of the following.

Military Radar
RF Newbie building a new toy
TV tower sending out a bad signal
Christmas lights turned on during the spring/summer
Old bad Florescent Light Ballast producing bad RF
Electronic Music Box with no FCC approvals turned on infrequently
Something else that I can fathom!!!

Question: How would I "shield the affected unit" as suggested??
Tin Foil around the opener??
Tin Foil over the wireless door transmitter??
Place a metal box over the antenna on the security receiver??

How is that going to determine if the interference was radiated or
conducted??

Thanks for any input!!

Les

On 7/17/2021 9:14 PM, ABLE1 wrote:
> On 7/17/2021 5:19 PM, Don Y wrote:
> > On 7/17/2021 6:07 AM, ABLE1 wrote:
> >> Hello, I find this VERY interesting.  I won't go into the whole story
> >> since it is very long but I have a customer that has an alarm system
> >> that I installed.  It has wireless sensors for doors and such.
> >> There has been a few times that the system does not receive signals
> >> from the transmitters for periods of time from 45 minutes to 2 days.
> >
> > 2 *days*?  Are you sure someone isn't (illegally) operating
> > a transmitter, nearby?
> >
> That is a possibility.  Again finding and proving is the challenge.
>
>
>
> >> During this time their garage door opener remote does not work unless
> >> you hold it in you hand reach up to within 18" of the opener antenna
> >> and then it will work.
> >>
> >> During that time the problem or source can't be determined.
> >> In discussions with neighbors it has be determined that at least
> >> 4 others, next door and across the street have experienced the same
> >> with there openers.
> >>
> >> Then it all stops and goes back to normal operation???
> >>
> >> This happened about 2 years ago and then again about a month ago.
> >> That I know about that is.
> >>
> >> Needless to say when it IS NOT happening it is absolutely impossible
> >> to find.  When it IS happening it is absolutely impossible to find.
> >>
> >> The openers have a red LED on the unit that is used for learning in
> >> a remote button.  Normally it is off until it receives a signal from
> >> a remote to open.  During these events the LED is solid red for the
> >> entire time frame.  Then during the end of the event it starts to
> >> flicker and then off.
> >
> > Verify the *complete* behavior of the indicator.  Usually, when
> > in "learn mode" (activated by a button on the RECEIVER), the
> > indicator will flash (until it times out).
> >
> > Some flash when they detect an obstacle in the path of the door
> > (either photoelectrically or by sensing an increased current
> > draw by the motor)
> >
> > Does "lit" coincide with the *entire* open/close cycle?  I.e.,
> > the behavior you are seeing SHOULD be accompanied by the door
> > moving (?)
> >
> This LED is primary for learning in a remote.  And just blinks when the
> remote is pushed. Which is seeing the RF Signal.  Normally the LED
> is off.  During my observation at the 45 minute period.  The handheld
> remote would not work unless it was held up within 18" of the antenna.
> Also the Subaru header button did not work.  There were two house doors
> that would not communicate the doors were open or closed to the security
> panel during this time.  At the same time the next door neighbor's
> garage remote would not work.  Then the LED started to blink and then
> off.  Door contacts then worked as they should.  The event was over
> and as I am aware has not returned.
>
>
> >> The security devices are on 319.5 Mhz and the door opener is on 318
> Mhz.
> >>
> >> Is there any thoughts here as to what other than Military Radar that
> >> could be causing this issue with such intensity in a small area??
> >
> > Almost anything can be an "unintentional radiator" -- even things like
> > christmas lights!
> >
> > I'd wonder if someone wasn't (naively) putting a bunch of hash out.
> > The "45 minutes" sounds like someone might be "doing something"
> > (or USING something) for a short period.  The "2 days" suggests it
> > got left *on*!
> I agree, but when it is not on it can't be found.
>
>
> > I lived in a house with the garage located beneath the master bedroom.
> > Vacuuming the carpet in the MBR would often result in the garage door
> > opening.  We'd come out, the next morning, to leave for work and
> > wonder which of us had "*left* the door open"!  (Ans:  neither)
> >
> >> There is a local airport with control tower about 2 miles away.
> >
> > Possible.  Why not go sniffing for signals?  TV or radio stations
> > nearby?
> No Radio or TV nearby. Closest TV station is 6 miles as the crow flies.
> But I would think that if something that far away would have a much
> broader area effected rather than this very small area of maybe 6 homes.
> At least that I know about at this time.
>
> It would make more sense that what ever it is would be located in
> one of the nearby houses that is radiating out 306 degrees, but What??
> And Where??
>
> >
> >> I say a small area (200' square box maybe??) but it could be effecting
> >> a larger area but I have no way to know or to find out without having
> >> a town meeting.
> >>
> >> Any thoughts on the subject would be most helpful.
> >
> > When the problem next manifests, try to shield the affected unit.
> > This would at least give you an idea if the interference was radiated
> > or conducted.  In most places, several homes are fed from a single
> > transformer.  So, your line is a direct reflection of what's happening
> > in your neighbor's homes.  Neighbors served by *another* transformer
> > will have two transformers acting to attenuate signals between your
> > home and theirs.
> >
> > [Here, it's 4 homes per xformer -- and I can easily deduce which
> homes are
> > serviced "together" (or service is all below grade)]
> This a new 55 and over community that was new in the past 3 years or so.
> Houses are rather close and streets are narrow.  As things always seem
> to go it was first thought that the new security system that I was
> installing was the cause of the problem with the Door Opener.........
>
> I have more time in this problem trying to find the source or just
> pondering the problem than I want to think about.  Total LO$$!!
>
> It is horrible when you can't measure it, see it, touch it, taste it
> or even smell it!!!
>
> BTW I may have forgotten to mention that there are two Door Openers in
> this house and both react exactly the same way.
>
> From what I gather at this time is that it may be one of the following.
>
> Military Radar
> RF Newbie building a new toy
> TV tower sending out a bad signal
> Christmas lights turned on during the spring/summer
> Old bad Florescent Light Ballast producing bad RF
> Electronic Music Box with no FCC approvals turned on infrequently
> Something else that I can fathom!!!
>
> Question: How would I "shield the affected unit" as suggested??
> Tin Foil around the opener??
> Tin Foil over the wireless door transmitter??
> Place a metal box over the antenna on the security receiver??
>
> How is that going to determine if the interference was radiated or
> conducted??
>
> Thanks for any input!!
>
> Les

boB wrote:

Buy one of those $50 (ish) Tiny SA Spectrum alalyzers and see if
there is any RF signals around that frequency above the level there is
when the door IS working and compare.

That would tell you something. Then you could either get a
directional antenna for it or possibly drive around the neighborhood
trying to find where the signal gets stronger.

But first you need to see if nearby RF interference is even the issue
and what it looks like.

I wonder if there are any high power transmitter near by on another
frequency that could de-sense this garage door receiver ? Overload,

boB

===================================================================
I got a $20 (ish) thingie that has a colored LED bar when RF is
detected. It has a adjustment knob that you can dial up or down the
signal strength. Presently the customer has it but the nasty is not
going on so using it doesn't find anything other than the microwave is
turned on and it lights up when close.

The challenge is that it may not happen for another 2 years. Really
difficult/impossible to find the source when it's not there.

Thanks for the input!!

Les

On 7/17/2021 6:14 PM, ABLE1 wrote:
> On 7/17/2021 5:19 PM, Don Y wrote:
> > On 7/17/2021 6:07 AM, ABLE1 wrote:
> >> Hello, I find this VERY interesting. I won't go into the whole story
> >> since it is very long but I have a customer that has an alarm system
> >> that I installed. It has wireless sensors for doors and such.
> >> There has been a few times that the system does not receive signals
> >> from the transmitters for periods of time from 45 minutes to 2 days.
> >
> > 2 *days*? Are you sure someone isn't (illegally) operating
> > a transmitter, nearby?
> >
> That is a possibility. Again finding and proving is the challenge.

You need to go on a snipe hunt! :>

(seriously, though) Don't rule out something that shouldn't exist
(i.e., illegal or undesirable). Remember, there are lots of things
that are legit but that have to take measures to mitigate their
interference *if* they are interfering (this inherently assumes
there WILL be such things!)

In the 80's, a neighbor once inquired, "What the hell have you got
in there?" (meaning my house). I looked at him, puzzled. Apparently,
when he'd drive by, his scanner (?) would unsquelch with lots of
hash. At the time, everything that I had was COTS gear (though a
fair bit of it!) so I didn't feel like it was something I'd *designed*
that was giving him grief.

> >> During this time their garage door opener remote does not work unless
> >> you hold it in you hand reach up to within 18" of the opener antenna
> >> and then it will work.
> >>
> >> During that time the problem or source can't be determined.
> >> In discussions with neighbors it has be determined that at least
> >> 4 others, next door and across the street have experienced the same
> >> with there openers.
> >>
> >> Then it all stops and goes back to normal operation???
> >>
> >> This happened about 2 years ago and then again about a month ago.
> >> That I know about that is.
> >>
> >> Needless to say when it IS NOT happening it is absolutely impossible
> >> to find. When it IS happening it is absolutely impossible to find.
> >>
> >> The openers have a red LED on the unit that is used for learning in
> >> a remote button. Normally it is off until it receives a signal from
> >> a remote to open. During these events the LED is solid red for the
> >> entire time frame. Then during the end of the event it starts to
> >> flicker and then off.
> >
> > Verify the *complete* behavior of the indicator. Usually, when
> > in "learn mode" (activated by a button on the RECEIVER), the
> > indicator will flash (until it times out).
> >
> > Some flash when they detect an obstacle in the path of the door
> > (either photoelectrically or by sensing an increased current
> > draw by the motor)
> >
> > Does "lit" coincide with the *entire* open/close cycle? I.e.,
> > the behavior you are seeing SHOULD be accompanied by the door
> > moving (?)
>
> This LED is primary for learning in a remote. And just blinks when the
> remote is pushed. Which is seeing the RF Signal.

But, it is likely a processor/sequencer that is driving the LED; not
an "RF detector". (?) So, one has to wonder what assumptions went into
that design aspect.

I.e., if you use a WRONG remote (when the interference is not present)
and hold the remote actuated, does the LED stay lit? I.e., indicating
RF even though it is not CORRECT RF?

> Normally the LED
> is off. During my observation at the 45 minute period. The handheld
> remote would not work unless it was held up within 18" of the antenna.
> Also the Subaru header button did not work. There were two house doors
> that would not communicate the doors were open or closed to the security
> panel during this time. At the same time the next door neighbor's garage
> remote would not work. Then the LED started to blink and then
> off. Door contacts then worked as they should. The event was over
> and as I am aware has not returned.

You need to understand the criteria that cause the LED to illuminate.
Not just the *intended* criteria but the ACTUAL criteria -- as it is
the only EASY indicator to which you have access.

You're still going to need to go on a snipe hunt. If you had a spare
GDO ("parts"), you could wire the controls to a battery and wander around
the neighborhood using the LED as your crude indicator.

A better solution is to just get proper kit and do it right.
If you find an "offender", lodging a complaint will likely
have more standing if you can say "he was putting out X at Y MHz"
instead of "my GDO didn't work because of something I *think*
he was doing"

> >> The security devices are on 319.5 Mhz and the door opener is on 318 Mhz.
> >>
> >> Is there any thoughts here as to what other than Military Radar that
> >> could be causing this issue with such intensity in a small area??
> >
> > Almost anything can be an "unintentional radiator" -- even things like
> > christmas lights!
> >
> > I'd wonder if someone wasn't (naively) putting a bunch of hash out.
> > The "45 minutes" sounds like someone might be "doing something"
> > (or USING something) for a short period. The "2 days" suggests it
> > got left *on*!
> I agree, but when it is not on it can't be found.

Capture the available data when you can -- even the "normal" situation
may reveal an offender some N dB down! Without any real data, you're
just "complaining" and hoping something else identifies (or eliminates)
the problem.

> > I lived in a house with the garage located beneath the master bedroom.
> > Vacuuming the carpet in the MBR would often result in the garage door
> > opening. We'd come out, the next morning, to leave for work and
> > wonder which of us had "*left* the door open"! (Ans: neither)
> >
> >> There is a local airport with control tower about 2 miles away.
> >
> > Possible. Why not go sniffing for signals? TV or radio stations
> > nearby?
> No Radio or TV nearby. Closest TV station is 6 miles as the crow flies.
> But I would think that if something that far away would have a much
> broader area effected rather than this very small area of maybe 6 homes.
> At least that I know about at this time.
>
> It would make more sense that what ever it is would be located in
> one of the nearby houses that is radiating out 306 degrees, but What??
> And Where??

Ask yourself what the afflicted homes share in common.
Note that one of the "victims" may, in fact, turn out to be the
*culprit*!

> >> I say a small area (200' square box maybe??) but it could be effecting
> >> a larger area but I have no way to know or to find out without having
> >> a town meeting.
> >>
> >> Any thoughts on the subject would be most helpful.
> >
> > When the problem next manifests, try to shield the affected unit.
> > This would at least give you an idea if the interference was radiated
> > or conducted. In most places, several homes are fed from a single
> > transformer. So, your line is a direct reflection of what's happening
> > in your neighbor's homes. Neighbors served by *another* transformer
> > will have two transformers acting to attenuate signals between your
> > home and theirs.
> >
> > [Here, it's 4 homes per xformer -- and I can easily deduce which homes are
> > serviced "together" (or service is all below grade)]
> This a new 55 and over community that was new in the past 3 years or so.
> Houses are rather close and streets are narrow. As things always seem
> to go it was first thought that the new security system that I was installing
> was the cause of the problem with the Door Opener.........
>
> I have more time in this problem trying to find the source or just
> pondering the problem than I want to think about. Total LO$$!!

Customers... gotta love 'em! (not!)

> It is horrible when you can't measure it, see it, touch it, taste it
> or even smell it!!!
>
> BTW I may have forgotten to mention that there are two Door Openers in
> this house and both react exactly the same way.
>
> From what I gather at this time is that it may be one of the following.
>
> Military Radar

Or radio

> RF Newbie building a new toy

Or, some COTS bit of kit that was shoddily made, operated with
it's covers off, etc.

On 18/07/2021 02:14, ABLE1 wrote:
> On 7/17/2021 5:19 PM, Don Y wrote:
> > On 7/17/2021 6:07 AM, ABLE1 wrote:
> >> Hello, I find this VERY interesting.  I won't go into the whole story
> >> since it is very long but I have a customer that has an alarm system
> >> that I installed.  It has wireless sensors for doors and such.
> >> There has been a few times that the system does not receive signals
> >> from the transmitters for periods of time from 45 minutes to 2 days.
> >
> > 2 *days*?  Are you sure someone isn't (illegally) operating
> > a transmitter, nearby?
> >
> That is a possibility.  Again finding and proving is the challenge.

One cheap way would be to buy one of the TV tuner dongles that can be
subverted with suitable free software into a broadband SDR with a
waterfall display that will show you if there is anything jamming the
band used by your garage door TX. Or for that matter any very strong
signals that might overload the front end of its receiver.

That several neighbours have the same problem suggests local RF
interference jamming the door opener signal. It might be possible to
move your transmitters close enough to the receiver to overcome it.
> It would make more sense that what ever it is would be located in
> one of the nearby houses that is radiating out 306 degrees, but What??
> And Where??

What is allowed on that frequency in the USA?

--
Regards,
Martin Brown

On 7/18/2021 5:36 AM, Martin Brown wrote:
> TV tuner dongles that can be subverted with suitable free software into
> a broadband SDR with a waterfall display

TV tuner dongles that can be subverted with suitable free software
into a broadband SDR with a waterfall display

That is totally over my head.

I am sure it may be simple....................?? But??

If this issue were happening frequently or on some schedule putting
together some kind of tracking device may be a way. But with the
present condition of all is good, that can't happen.

Thanks,

Les

On 7/18/2021 12:38 AM, Don Y wrote:
> But, it is likely a processor/sequencer that is driving the LED; not
> an "RF detector".  (?)  So, one has to wonder what assumptions went into
> that design aspect.
>
> I.e., if you use a WRONG remote (when the interference is not present)
> and hold the remote actuated, does the LED stay lit?  I.e., indicating
> RF even though it is not CORRECT RF?

Very good thought!! I will try that the next time I am in the area.
Won't find the problem, but will give more information or input.

Thanks,

Les

On 7/18/2021 12:38 AM, Don Y wrote:
>
> Ask yourself what the afflicted homes share in common.
> Note that one of the "victims" may, in fact, turn out to be the
> *culprit*!

Good point!! Now that the "neighbor's" have been discussing the
situation that is happening, it is possible the "offender" is now
aware and had stopped or fixed the issue. That would be GREAT!!

Although then it will never be known what or who was causing it!!

And at that point it really doesn't matter anymore.

At least I can sleep nights!!

Thanks!!

Les

On 18/07/21 13:07, ABLE1 wrote:
> On 7/18/2021 5:36 AM, Martin Brown wrote:
>> TV tuner dongles that can be subverted with suitable free software into a
>> broadband SDR with a waterfall display
>
>  TV tuner dongles that can be subverted with suitable free software into a
> broadband SDR with a waterfall display
>
> That is totally over my head.
>
> I am sure it may be simple....................??  But??

One of many starting points:
https://www.rtl-sdr.com/about-rtl-sdr/

On 7/18/2021 5:18 AM, ABLE1 wrote:
> On 7/18/2021 12:38 AM, Don Y wrote:
>>
>> Ask yourself what the afflicted homes share in common.
>> Note that one of the "victims" may, in fact, turn out to be the
>> *culprit*!
>
> Good point!! Now that the "neighbor's" have been discussing the
> situation that is happening, it is possible the "offender" is now
> aware and had stopped or fixed the issue. That would be GREAT!!

They may not be aware that they are *still* doing it. If it
was happening *daily* at 3AM, would anyone know?

> Although then it will never be known what or who was causing it!!
>
> And at that point it really doesn't matter anymore.
>
> At least I can sleep nights!!

Oh, nights are for *work*! :>

On 18/07/2021 14:22, Tom Gardner wrote:
> On 18/07/21 13:07, ABLE1 wrote:
>> On 7/18/2021 5:36 AM, Martin Brown wrote:
>>> TV tuner dongles that can be subverted with suitable free software
>>> into a broadband SDR with a waterfall display
>>
>>   TV tuner dongles that can be subverted with suitable free software
>> into a broadband SDR with a waterfall display
>>
>> That is totally over my head.
>>
>> I am sure it may be simple....................??  But??
>
> One of many starting points:
> https://www.rtl-sdr.com/about-rtl-sdr/

And it is almost as simple as read the URL download the software and run
it. Bit of a learning curve but the display is easy to understand.

US Amateur Radio mags probably review slightly more user friendly
versions that cost a bit more and make it more or less plug and play.
(UK ones do anyway)

--
Regards,
Martin Brown

On 7/18/2021 9:22 AM, Tom Gardner wrote:
> On 18/07/21 13:07, ABLE1 wrote:
>> On 7/18/2021 5:36 AM, Martin Brown wrote:
>>> TV tuner dongles that can be subverted with suitable free software
>>> into a broadband SDR with a waterfall display
>>
>>   TV tuner dongles that can be subverted with suitable free software
>> into a broadband SDR with a waterfall display
>>
>> That is totally over my head.
>>
>> I am sure it may be simple....................??  But??
>
> One of many starting points:
> https://www.rtl-sdr.com/about-rtl-sdr/

Ok as a "starting point". Just doing a search on "rtl sdr"
brings up the following link on eBay.

https://www.ebay.com/sch/i.html?_from=R40&_nkw=rtl+sdr&_sacat=1500&rt=nc&LH_PrefLoc=1

Not that I am going to do this but out of 525 possible choices
which one might be the best choice??

This is all rather foreign to me.

Thanks,

Les

On 18/07/21 15:42, ABLE1 wrote:
> On 7/18/2021 9:22 AM, Tom Gardner wrote:
>> On 18/07/21 13:07, ABLE1 wrote:
>>> On 7/18/2021 5:36 AM, Martin Brown wrote:
>>>> TV tuner dongles that can be subverted with suitable free software into a
>>>> broadband SDR with a waterfall display
>>>
>>>   TV tuner dongles that can be subverted with suitable free software into a
>>> broadband SDR with a waterfall display
>>>
>>> That is totally over my head.
>>>
>>> I am sure it may be simple....................??  But??
>>
>> One of many starting points:
>> https://www.rtl-sdr.com/about-rtl-sdr/
>
>
> Ok as a "starting point".  Just doing a search on "rtl sdr"
> brings up the following link on eBay.
>
> https://www.ebay.com/sch/i.html?_from=R40&_nkw=rtl+sdr&_sacat=1500&rt=nc&LH_PrefLoc=1
>
>
> Not that I am going to do this but out of 525 possible choices
> which one might be the best choice??
>
> This is all rather foreign to me.
>
> Thanks,
>
> Les

R820T2 is a good starting point.

They are a commodity item, all much of a muchness and suitable
for casual use.

There are some with a lower noise floor, but they are more
expensive and change over time. A metal case helps.