frequencies below fm

Everything technical about radio can be discussed here, whether it's transmitting or receiving. Guides, charts, diagrams, etc. are all welcome.
Post Reply
User avatar
radionortheast
tower block dreamin
tower block dreamin
Posts: 316
Joined: Wed Sep 09, 2015 1:38 pm

frequencies below fm

Post by radionortheast » Sat Apr 27, 2019 10:09 am

Hi, I just thought I would ask, are there any services which still use frequencies below the fm band? my tx can tune down there if I set it to the Japanese band, my little radio can tune there, I was thinking it might be safer to operate down there, as no one could eavesdrop on it.

User avatar
McDonalds
tower block dreamin
tower block dreamin
Posts: 341
Joined: Fri Aug 29, 2014 12:20 pm
Location: Essex UK
Contact:

Re: frequencies below fm

Post by McDonalds » Sat Apr 27, 2019 12:17 pm


radium98
tower block dreamin
tower block dreamin
Posts: 319
Joined: Fri Aug 26, 2016 7:01 pm

Re: frequencies below fm

Post by radium98 » Sun Apr 28, 2019 5:53 pm

i am always linking on 85.5 with tx veroxxx 20w and as rx as use onkyo tuner 76 to 89.9 mhz or just increse value of xtal from 4.5 to 4mhz to shift the band down but you might not have correct radio frequency display reading
exemple you read 87.5mhz and you will receive 85.5 mhz

nrgkits.nz
no manz can test innit
no manz can test innit
Posts: 187
Joined: Fri Oct 17, 2014 10:35 am

Re: frequencies below fm

Post by nrgkits.nz » Tue Apr 30, 2019 2:11 am

I would excercise caution operating any transmitter below 87.5MHz, I don’t know about the UK but here in NZ this part of the spectrum known as A band is full of radio telephones used by taxis, couriers and even police and the fire service - no one wants to interfere with emergency comms, you’ll get a lot more than a knock on the door! Note that RT transmitters/repeaters only transmit when someone holds the push to talk button on their RT so hearing just dead static on a particular frequency doesn’t mean that it’s not being used. You would be best to check which licenses have been assigned (probably a request of some description to Ofcom) if you do decide to try and use this part of the band and avoid being within 400KHz of any assigned comms channel and avoid the freq range completely if it’s being used by emergency services.

Albert H
proppa neck!
proppa neck!
Posts: 1220
Joined: Tue Apr 05, 2016 1:23 am

Re: frequencies below fm

Post by Albert H » Wed May 01, 2019 10:33 am

Band I used to be a good choice for links, but not any more. The aerials are huge (and obvious), and most of the old Band I TV aerials have been taken down off roofs.....

Smart people use Band IV or V for linking. You can find huge open spaces now that the analogue TV has been switched off. Also, you can use ordinary TV Yagis at each end - a telly aerial never looks out of place! With a reasonable receiver, a few hundred milliwatts of transmit and a couple of high gain Yagi TV aerials, you can link tens of kilometres! Receivers are quite easy if you use the TV front end modules that are cheaply available from any company that supplies TV spares (look in "Television" magazine). The transmit part is a little trickier, since every component lead or PCB track shows significant inductance (and some capacitance effects too) at these frequencies.
"Why is my rig humming?"
"Because it doesn't know the words!"
;)

User avatar
radionortheast
tower block dreamin
tower block dreamin
Posts: 316
Joined: Wed Sep 09, 2015 1:38 pm

Re: frequencies below fm

Post by radionortheast » Mon May 20, 2019 10:09 am

i've decided it might be too effy to put something down there, :) I think I more worry about it been out of band it been flagged up some where. I did used to hear walkie talkies my radio going quiet when tuned to 87.5, I never got them on my scanner, but did ruffly know were they where coming from, 2 different groups each about 10 miles away, i've not heard them in quite a few years, I guess they must of switched over to something else like 446, all the scanner lists of frequencies are old.

Albert H
proppa neck!
proppa neck!
Posts: 1220
Joined: Tue Apr 05, 2016 1:23 am

Re: frequencies below fm

Post by Albert H » Mon May 20, 2019 1:37 pm

I really would suggest that you consider the old analogue TV bands. There's not a lot there at the moment, and you should be able to find a nice quiet spot for your link. Use a couple of TV aerials, and you're good to go.

A friend of mine wanted to link about 300m - pretty much across the road - to a nearby high building. He used Band IV Yagi TV aerials at each end, and a cheap Chinese video / audio modulator unit (the type they use for cable distribution in blocks of flats) for the transmitter, and the receiver was an old portable analogue TV - just using the sound output. It worked really well, and cost virtually nothing to assemble.
"Why is my rig humming?"
"Because it doesn't know the words!"
;)

ronald001
who u callin ne guy bruv
who u callin ne guy bruv
Posts: 17
Joined: Sun Jan 17, 2016 1:49 pm
Location: Netherlands

Re: frequencies below fm

Post by ronald001 » Wed May 22, 2019 3:47 pm

Over here ( NL ) the "japanese band" is used among pirates for wideband DX.
DRFS and amateurradioshop sell their kits nowadays standard with a pic suitable for 85-110Mhz

Some guys are very skilled with modifing tuners.
They found a way to set EU tuners to japanese mode + changing the varicap for correct operation of the tuner in this band

radium98
tower block dreamin
tower block dreamin
Posts: 319
Joined: Fri Aug 26, 2016 7:01 pm

Re: frequencies below fm

Post by radium98 » Fri May 24, 2019 9:59 pm

agree with ronald001 ,only i said shift down a half meg the xtal of tuner and is enough
i have the hex 85-110 if anyone need

bristolpirates
tower block dreamin
tower block dreamin
Posts: 299
Joined: Tue Sep 16, 2014 8:21 pm

Re: frequencies below fm

Post by bristolpirates » Sat May 25, 2019 10:56 am

ronald001 wrote:
Wed May 22, 2019 3:47 pm
Over here ( NL ) the "japanese band" is used among pirates for wideband DX.
DRFS and amateurradioshop sell their kits nowadays standard with a pic suitable for 85-110Mhz

Some guys are very skilled with modifing tuners.
They found a way to set EU tuners to japanese mode + changing the varicap for correct operation of the tuner in this band
I've just read that there were rumors going around in about 2007 of Polish pirates in London using the OIRT / UKV band. Not sure if it's true, or if anybody knows anything about this on here.

User avatar
teckniqs
proppa neck!
proppa neck!
Posts: 2126
Joined: Thu Aug 21, 2014 11:37 am

Re: frequencies below fm

Post by teckniqs » Sat May 25, 2019 12:37 pm

You need to be careful using 64 to 87.5MHz as depending where you are located, there could be a lot of PMR/Taxis using it around there.
In the late 90s I had an analogue tuner which went slightly below 87.5 and all I could hear with it right down there was taxis, even on 87.5 sometimes.

nrgkits.nz
no manz can test innit
no manz can test innit
Posts: 187
Joined: Fri Oct 17, 2014 10:35 am

Re: frequencies below fm

Post by nrgkits.nz » Sat May 25, 2019 1:54 pm

Here in NZ we could hear the police around 78MHz on a Japanese radio, (most cars in NZ are imports from Japan), or around 486MHz using a scanner, that was back around 2010, now they have all moved to digital encryption.

Post Reply