Garda on 2.4 GHz ??

tenox

Hi,

Some people around Dublin have problems when flying model airplanes at 2.4 GHz. Interferences or loosing controll all together. Same problems with wireless video. So I've got my receiver and went to 2400 MHz and what I hear: 2457.700 MHz narrow FM -> a Garda dispatcher.

Is that Garda?
Are they sane? 2400 is almost like a public band.
Why won't they start using CB radio or FRS/GMRS walkie talkies you can buy in Tesco?

Is there something wrong with me?
Cheers,

watty

Wireless video etc is interfered with by WiFi (same band).
Bluetooth also uses 2.4GHz.

I'd say your scanner has poor image frequency or IF rejection. The Garda don't use 2.4GHz for voice.

WiFi is most likely issue for you Airplane woes.

If you post what model of scanner you used, we might identify the actual frequency it was receiving.

tenox

I know WiFi and Bluetooth are on 2.4GHz so are microwave ovens and many many more things. The issue is not with video which I can switch to another frequency in that band, but with radio controllers (transmitters) which you can't. But this is not my question to the forum. ISM band devices are required to deal with interferences and other transmissions themselfs and if they don't, well tuff .... they don't comply with the requirements.

My question was what is Garda doing on 2457.700 MHz (also 800)?

They talk exacly like the other Garda on aroud 455 MHz and they talk about things only Garda can talk about. I can send you some recordings if you wish (I don't belive recordings if ISM band are a crime especially if investigating an interference). But best if you go to that freq yourself and check it out.

There are several other voice dispatcher services, some trunked, but my question is specifically about Garda.

My receiver is ICOM PCR-2500 but I also have IC-R3.

Thanks,

watty wrote: »

Wireless video etc is interfered with by WiFi (same band).
Bluetooth also uses 2.4GHz.

I'd say your scanner has poor image frequency or IF rejection. The Garda don't use 2.4GHz for voice.

WiFi is most likely issue for you Airplane woes.

If you post what model of scanner you used, we might identify the actual frequency it was receiving.

humaxf1

probably an odd ball harmonic?

do you live near "control" by any chance? might be picking up spurious spatter!?

which particular part of dublin does this happen in?

tenox

This is near Tallaght and through the mountains towards Blessington, along N81 and near Red Cow.

This is several channels separated by 100 khz and the signal is really strong.

humaxf1 wrote: »

probably an odd ball harmonic?

do you live near "control" by any chance? might be picking up spurious spatter!?

which particular part of dublin does this happen in?

watty

It could be a 7th, 9th harmonic or such. The real channel spacing is thus 100/9 kHz etc depending on harmonic.

They absolutely don't use 2.4GHz.

tenox

Yeah, must be a harmonic. I can hear the same sources as on the fundamental frequency of 455-456 MHz just shifted little bit. The reception is unbelievably strong though.

watty

A rusty bolt the "wrong size" on TX mast/aerial, or cheap nickle plated connector can do it!

tenox

Also how come there is so many (4-5 commercial) dispatcher stations doing same (except much lover signal level).

How is that I can also hear individual Garda officers from their mobile walkie talkies?

Thanks a lot.

watty

You're hearing a repeater on a high site?

Tactical

Of course it could also be someone using 2.4GHz as a link from a scanner in a more favourable location to beam the audio back to a receiver?

I know several people in poor locations who mount a scanner up high with a battery and a 2.4GHz txmitter. They only need to change the battery onec a week or so.

That way they can hear anything the scanner can, without being physically present at the scanner. Not quite a repeater but a point to point one way link.

gerryk

tenox wrote: »

Is there something wrong with me?

More likely your receiver is at fault. As watty said, it probably has poor image rejection. Being a wideband receiver, by definition it will have a wide front end, and unless it's an expensive model, is unlikely to have any switchable band pass filtering.
Also, little hand held scanners and so are generally made to be used with the little whips they're provided with and will overload badly if connected to an external antenna. I had a Yupiteru MVT7100, which is an excellent scanner with great sensitivity, but connected to a discone, it became a magnet for pager signals... they'd break squalch all over the VHF band, regardless of actual frequency.