frequencies below fm

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radionortheast
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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.

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Re: frequencies below fm

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


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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

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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.

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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.
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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.

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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.
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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

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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

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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.

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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.

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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.

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Re: frequencies below fm

Post by ronald001 » Mon May 27, 2019 10:32 am

According to the OFCOM website, 80 - 87.5 Mhz is allocated for the following:

UK12 - Specific details of frequencies for Distress and Safety, Search and Rescue and Emergencies are contained in the document "Frequencies for Distress and Safety, Search and Rescue and Emergencies in the UK".
UK27 - Services for Programme Making and Special Events (PMSE) assignments and authorised by Ofcom for some frequencies in this band, and may be subject to coordination with the Ministry of Defence. Where coordination is required, assignments are made on a non-protection non-interference basis.
UK6 - The use of Industrial, scientific and medical (ISM) applications is allowed in this band providing they do not contravene the provisions of the Wireless Telegraphy Act 2006. Radiocommunication services must accept harmful interference from these devices.
UK5.3 - 80 - 83.5 MHz and 85 - 87 MHz Ofcom for civil use. 83.5 - 85 MoD for military use. Resident Emergency Service use in Scotland in selected channels in 80 - 81.5 MHz.
UK2.1 - Responsibility for granting permissions to use frequencies in this Allocation rests with Defence. All frequency permissions are reserved exclusively for Defence use except where assignments for Civil use are agreed with Ofcom.
UK1.1 - Responsibility for assigning frequencies to this Allocation rests with Ofcom. Frequencies in this Allocation are exclusively assigned for civilian use. Exceptionally, Ofcom may agree to the use of these frequencies for military purposes with the Ministry of Defence.
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Re: frequencies below fm

Post by SamTheDog » Mon Jun 17, 2019 5:03 pm

It's not a good idea to use the 68-88 MHz section. All sorts of legitimate users occupy this band and they are likely to complain if they get interferance on thier service....

I have 45-55 MHz kit if I need to use that band...... At a push it will even go onto the proper J F M G allocations too.....
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Re: frequencies below fm

Post by Albert H » Wed Jun 19, 2019 2:21 am

For a long time, one station I built gear for used 58.7MHz as their link frequency - the receive crystals were really cheap (48 MHz!). They had about half a Watt going into a horizontal dipole, with an old Band 1 TV aerial used at the main TX end! The receivers were really simple - bipolar transistor RF amp, single-gate FET mixer, bipolar transistor crystal injection oscillator and a CA3089 IF chip. These simple links worked well over two or three kilometres.
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