70MHz antenna

A place to discuss all aspects of amateur radio operation.
User avatar
Werthers
Super Member
Super Member
Posts: 306
Joined: 01 Sep 2019, 20:19
Location: Essex

70MHz antenna

Post by Werthers » 12 Oct 2019, 16:36

I'm planning on building a 70MHz antenna for 4 meters and I'm not allowed to install any antennas outside neither do I have access to my roof whatsoever and I do not have a garden.

I use to have an indoor dipole indoors which pretty much dominated the room it was in and wasn't really a permanent setup anyway not to mention being a pain as it got in the way of everything, however it did perform well. I don't have that dipole anymore as my ex girlfriend snapped it up a while back.

I have a small loft so I'm limited for space and I have done some measurements of the loft to see what is possible.

A half wavelength is just under 7 foot although the loft is only about 5 foot high so putting a dipole up vertical wont fit so it will have to be somewhat horizontal and I'm thinking of a V or L shaped dipole antenna which will fit. I'll mainly be working FM.

Here is a few bits I've ordered to start things off.

I'd really appreciate any ideas or advice.
You do not have the required permissions to view the files attached to this post.

User avatar
Werthers
Super Member
Super Member
Posts: 306
Joined: 01 Sep 2019, 20:19
Location: Essex

Re: 70MHz antenna

Post by Werthers » 12 Oct 2019, 19:17

Well after doing some thinking my idea of the 70MHz dipole in the loft probably wont perform that well if at all unless its a standard vertical dipole which still wont be the best but will work ok, but as I don't have the height in the loft I need for a vertical dipole for 70MHz its not going to happen.

I've been looking at a few antenna designs but they all require to be lengthy in order to be half decent.

There is the Viper Antenna which is available for 70MHz and its a wire antenna so its more practical for indoors and easy to take down and put away when I'm not using it and offers a 3.0 dbi gain however the only problem with the Viper antenna is that its just over 12 foot in length and my ceiling is 10 foot high from the floor... I could build a smaller version of the Viper antenna of course it wont fit in the loft and building a smaller version I'd lose some gain but would be easier to pin up. If I can achieve a 1.5 to 2 dbi gain then it be better than my other idea.

Also the only other antenna designs I've seen are the J-Pole and Slim-Jim designs which I don't like.

User avatar
DX-Digger
Radio Addict
Radio Addict
Posts: 801
Joined: 27 Jul 2009, 22:01
Call Sign: TM205
Location: ... - --- -.- . --- -. - .-. . -. -

Re: 70MHz antenna

Post by DX-Digger » 12 Oct 2019, 19:37

You could go for a 1/4 vertical with 4 x 1/4 radials that would work.
Or could you fit a Delta loop in the loft?
I use one on 6mtrs ok its outside but works very well.
Or a magnetic loop or a halo type antenna.
Anyway Just a few idea's
:thumbup:
ʎɐqǝ uo pɹɐoqʎǝʞ ɐ ʎnq ı ǝɯıʇ ʇsɐן ǝɥʇ sı sıɥʇ

User avatar
ch25
Radio Addict
Radio Addict
Posts: 751
Joined: 03 Dec 2016, 11:07
Call Sign: Lemmy
Location: Poland

Re: 70MHz antenna

Post by ch25 » 12 Oct 2019, 20:05

Werthers wrote:
12 Oct 2019, 16:36
I'm planning on building a 70MHz antenna for 4 meters and I'm not allowed to install any antennas outside neither do I have access to my roof whatsoever and I do not have a garden.
Don't bother than.
Chris
You can't have too many antennas...

User avatar
Werthers
Super Member
Super Member
Posts: 306
Joined: 01 Sep 2019, 20:19
Location: Essex

Re: 70MHz antenna

Post by Werthers » 13 Oct 2019, 09:05

DX-Digger wrote:
12 Oct 2019, 19:37
You could go for a 1/4 vertical with 4 x 1/4 radials that would work.
Or could you fit a Delta loop in the loft?
I use one on 6mtrs ok its outside but works very well.
Or a magnetic loop or a halo type antenna.
Anyway Just a few idea's
:thumbup:
The Delta loop sounds like the one to go for, I may even just about get away with a 1/2 wave Delta loop in a 5 foot high spacing :think:

I'll build a few antennas. The 1/2 Viper is easy to make as well which is basically a coax dipole that I could string up somewhere temporary while I work on a permanent setup for the loft. I will build the Delta loop as well and see how each antenna performs.

Luckily where I live I have got a good take off point with reasonably high elevation hence why I do well with indoor antennas.

I'll also need to find some half decent coax for the Viper build otherwise I could end up with this situation...
You do not have the required permissions to view the files attached to this post.
Last edited by Werthers on 13 Oct 2019, 09:44, edited 2 times in total.

User avatar
Werthers
Super Member
Super Member
Posts: 306
Joined: 01 Sep 2019, 20:19
Location: Essex

Re: 70MHz antenna

Post by Werthers » 13 Oct 2019, 09:12

ch25 wrote:
12 Oct 2019, 20:05
Werthers wrote:
12 Oct 2019, 16:36
I'm planning on building a 70MHz antenna for 4 meters and I'm not allowed to install any antennas outside neither do I have access to my roof whatsoever and I do not have a garden.
Don't bother than.
Chris
Thats not very positive now is it :D

Giving up is not an option, besides I could never give up my 4 Meters.

mr_m3
Super Member
Super Member
Posts: 422
Joined: 12 Jan 2008, 22:09

Re: 70MHz antenna

Post by mr_m3 » 13 Oct 2019, 19:31

1/4 wave and a ideal ground plane may work in your loft as already stated or a coil shortened dipole but it really depends on how much power you plan to run through it i suppose, a delta loop sounds appealing too
26TM069
M3UBO-----> 2E0FML

User avatar
Werthers
Super Member
Super Member
Posts: 306
Joined: 01 Sep 2019, 20:19
Location: Essex

Re: 70MHz antenna

Post by Werthers » 14 Oct 2019, 08:38

mr_m3 wrote:
13 Oct 2019, 19:31
1/4 wave and a ideal ground plane may work in your loft as already stated or a coil shortened dipole but it really depends on how much power you plan to run through it i suppose, a delta loop sounds appealing too
That would work but other antennas would have better results, I remember trying a 1/4 wave with a ground plane in the past and it worked but a dipole gave me better results, a shortened coiled dipole sounds interesting, running power in a small space wouldn't be ideal I could probably get away with about 10watts which is plenty. I'm going to go with a Delta Loop to start with as I can get a 1/2 wave up there which would offer some gain over a 1/4 wave with a ground plane.

User avatar
Werthers
Super Member
Super Member
Posts: 306
Joined: 01 Sep 2019, 20:19
Location: Essex

Re: 70MHz antenna

Post by Werthers » 15 Oct 2019, 09:47

I was unable to sleep last night for some reason so I decided to draw out some antenna designs and take more measurements and do lots of thinking. I've got almost everything I need for the build. I do need to clear out the junk in the loft as well, most of it is rubbish and the other stuff can go straight to the charity shop, so that's the first thing to do. .

I found this site that could prove to act as a useful tool for testing my range http://sdr.codedv.com:8091/ if I can see my signal show up on this webSDR then I know my signal is getting out.

I also need to carry out some tests as there had been solar panels fitted to the roof recently, hopefully not above where I'm going to be installing my antennas otherwise it could through a spanner in the works. I have a pipe finder somewhere that will detect metal in the roof and I can also see if I can find some birds eye views on my roof using google map image search, if that's the case I will have to re-think my antenna plans but one thing is for sure and that's I'm not giving up.

I've seen a few people in my time who gave up Amateur radio due to not being allowed to install any antennas to there roof. The Ham radio hobby will never leave me its just one of those hobbies that sticks. I've tried asking for permission before several times but I'm always told no which is very frustrating, and more frustrating that there isn't anybody who is not a Ham that understands about antennas or radio, I have been told in the past to use the communal TV antenna... yeah like that's going to work or a wire coat hanger :roll:

The key thing is to stay positive, I am in a better situation than some out there and as I've said before I have a good take off point where I am and do well with indoor antennas.

While I had been removing the junk from the loft I found a mobile modulator CB whip and that gave me an idea to build a horizontal dipole for 10 and 11 meters for AM/SSB operations, I will just need to order another which should fit nicely in the loft along with my 4 meter antenna so I'll be sorted then for 3 bands, I'll also be redoing my VHF/UHF setup.

I also have a future plan for a shortened coiled HF antenna for 80/40/20 meters. I already have a receiving HF antenna strung up along the ceiling so that will come down once I make the new antenna for HF.

First thing is first and that's to get my 4 meter antenna done.

User avatar
Werthers
Super Member
Super Member
Posts: 306
Joined: 01 Sep 2019, 20:19
Location: Essex

Re: 70MHz antenna

Post by Werthers » 15 Oct 2019, 14:59

The 4 Meter antenna is pretty much built I just need to find my coax I may need to order some more if I can't find it and I'll be making an RF choke from coax and PVC pipe I'm also working on a 10 meter antenna as well.

As for the solar panels on the roof... I had a look on google maps images and the solar panels are nowhere near which is good news.

I found this youtube video which I find interesting... I think there should be more videos like these and more talk about attic antennas because not everybody has the luxury of being allowed to have outdoor antennas. Here's the video https://www.youtube.com/watch?v=gFW-dre0OrQ

Heres another interesting attic antenna video https://www.youtube.com/watch?v=as5nVgicVxE absolutely incredible.

I do think this issue with antenna restrictions needs to be looked into more and explored as its a very big issue that a lot of Hams face especially those who have just past there foundation exam never to be heard again due to antenna restrictions and with the housing problem here in the UK many people are living in rented property also properties in general in the UK are more restricted in terms of space, not everybody has a garden or a balcony to work with.

I feel many aspects of the Ham radio hobby has been lost over the years. We live in a society where everything is handed to us on a plate ready to work right out of the box without any challenges or very little.

Lots of amazing things can still be done with indoor antennas, there is always away to get around problems and get on the air.

Amateur radio is a hobby that involves challenges and problem solving and antenna restrictions is one of those.

Every game has rules which is why we play them, so just think of antenna restrictions as a very good game that is fun we can play. There will always be limitations, you'll never have the perfect station, there's always going to be other Hams with better stations no matter which way you look at it. Its important to realize that Ham radio is not a competition, everybody is in a different situation and its important to work with what you have and make the best out of your limitations. You also learn a lot in the process.

The important thing is to get into the right mindset and never give up if the first thing you try doesn't work then keep trying, personally I'd go out of my way to help out another ham to get on the air who is in despair from antenna restrictions, we need more hams on the air in the UK, more people on the air means more activity on the bands, more enjoyment for all.

I've heard many people say don't bother with 4 meters its dead... 4 meters is not dead as some of us may already know and the same can be said about any band. The main problem is to many people listening and not enough people transmitting. All's it takes is two hams to make a band active. 4 meters is a very special band with a lot of potential thats often over looked.

User avatar
Werthers
Super Member
Super Member
Posts: 306
Joined: 01 Sep 2019, 20:19
Location: Essex

Re: 70MHz antenna

Post by Werthers » 18 Oct 2019, 22:38

Just an update... my roof was worked on some time ago, the bad news is its laced with foil and conductive roof tiles so I'm pretty much stuffed I'll just be limited to local repeater use on 2 meters and 70cm. DMR for worldwide contacts.

mr_m3
Super Member
Super Member
Posts: 422
Joined: 12 Jan 2008, 22:09

Re: 70MHz antenna

Post by mr_m3 » 19 Oct 2019, 22:45

couldn't you have it in a room with some free radiating space around it, i know i work friends on 2m with x30/50's indoors around 5-10 miles away
26TM069
M3UBO-----> 2E0FML

mr_m3
Super Member
Super Member
Posts: 422
Joined: 12 Jan 2008, 22:09

Re: 70MHz antenna

Post by mr_m3 » 19 Oct 2019, 22:46

what about some sort of fancy wonder whip for hf, they're very limited but you will make some contacts no doubt
26TM069
M3UBO-----> 2E0FML

mr_m3
Super Member
Super Member
Posts: 422
Joined: 12 Jan 2008, 22:09

Re: 70MHz antenna

Post by mr_m3 » 19 Oct 2019, 22:48

http://www.iw5edi.com/ham-radio/3313/wo ... ip-antenna

£10 build for a small antenna that you will be able to load onto almost every band, then see if you can get it in a window i suppose?
26TM069
M3UBO-----> 2E0FML

User avatar
Werthers
Super Member
Super Member
Posts: 306
Joined: 01 Sep 2019, 20:19
Location: Essex

Re: 70MHz antenna

Post by Werthers » 21 Oct 2019, 09:26

mr_m3 wrote:
19 Oct 2019, 22:45
couldn't you have it in a room with some free radiating space around it, i know i work friends on 2m with x30/50's indoors around 5-10 miles away
I used to do exactly this with indoor dipoles one for 2 meters and another for 4 meters and I did reasonably well I got about 30 miles out, I could have been doing a bit more but my longest distance contact was 20 miles on 2 meters and 30 miles on 4 meters so not bad for an indoor antenna under normal conditions. I can't achieve that now as the RF goes no further than the inside of my home since they worked on the roof. I can't even hear myself locally on the webSDR.

I do have some plans... I'm going to buy a Comet GP-1 antenna for VHF/UHF which I'll be installing to a pole that will then be fixed outside just by my window, so the antenna will be just above the start of the roof line even though I have antenna restrictions and was told no 3 years ago I'm just going to go ahead and put it up anyway and then see if I can fight the case if they tell me to take it down. I desperately need to improve my VHF/UHF setup because its absolutely pitiful the way it is now and I miss my simplex operations and nets and the only way to do it is getting something outside.

For the 70MHz antenna I'm going to try a 1/4 wave whip with some ground plane wires running to something, I've not thought it through yet but I'm thinking of ways how I can at least get the 1/4 wave part of the antenna just above the roof outside with it being stealthy as possible.

On another thread which is in the CB section I'm going to see if I can get away with having a CB antenna by poking a mobile CB whip through the roof between a gap where a stink pipe is which is still work in progress as its not quite as straight forward as that, I did think about doing the 70MHz the same way but having two antennas so close together I don't think would help so I can only do one in that space.

The good thing is the 70MHz antenna is much shorter with the whip being just over 3 foot, its more manageable to work with and easier to hide than a CB mobile whip.

Post Reply