hf longwire

[2e1var]

Short answer is yes but I wouldn't bother. Feed your coax to a 10m wire with a reasonable ground and you'll be fine.

[hregor]

Hi

I take it that you're a bit like me and want an aerial that works well on every frequency. The advantage we have is that we're only interested in receive. Most calculations in articles on aerials are usually concerned with transmitting, which is much more demanding and usually ends up with aerials that only work within 1 or 2% of their design frequency.

On receive, the reality is that almost any bit of wire will give you enough signal to work your receiver. You'll probably find that you can get RAF Volmet on 5450 just by poking your finger in the aerial socket.

The problem is not the strength of the signal but the noise that comes with it. Some of this is natural background noise which you can't do much about and is the eventual limiting factor.

Over the top of that is all the manmade rubbish radiating from every bit of electronics you can think of, from mobile phone chargers, computers, industrial plant, power lines etc. A lot of this is conducted via the house wiring. A tent by the sea in West Wales would be a good place to live.


What you need to do is place your aerial, even if it's just 3 metres of wire, as far away as possible from anything that's producing noise. Outside is good or in the loft, vertical if you're short of space. Your receiver is likely to be right in the centre of all the electrical noise, close to your computer and TV, so you need to connect the aerial to the receiver using screened coax cable.

At HF the losses are pretty minimal so you don't need anything like low loss coax but the screening is important. I've tried cheap TV coax and the screening is so bad that it picks up noise enroute from the aerial to the radio. In my experience satellite TV cable is much better, with its solid screen.

It's important that the coax screen is connected to the receiver's earth. At the aerial end, just connect the coax centre to the aerial.

Purists will argue that you need an aerial tuning unit between the aerial and the coax but in my experience doesn't always make much difference. You'd have to go out and retune it every time you moved frequency anyway, which is a pain.

Another point to watch is that you can have too much signal. This overloads the receiver and produces signals which don't actually exist, getting in the way of the real signal. Short aerials are good in this respect.

Every installation is unique, the key is to try different things looking for improvement, some people even get to like making aerials, sados like me.

As regards refueling 6761 is the US common, but it's not very busy. There are lots of other ineresting frequencies, Rich C has posted a long list in the FC HF section which would be worth a look at. In fact if you read through all the posts you'll get a good idea of what's out there.

Regards
Roger

[Sussex to Devon]

Hi,

A antenna tuner unit will give optimum results matching the aerial length to various Frequencies. The link will provide the calculations for the HF wire length for the frequency required.
Atu and HF cable length


Hope it helps.

Ian

[jingernut]

How high in the garden have you got it strung up?

[wave scanner]

Hi there Atcmanch,
just out of interest what model Icom reciever do you have?

[wave scanner]

oh right, I thought on that radio the n type was for above 30mhz and the so239 was for below 30mhz ?Although I'm not 100% sure.
I love icom recievers though.
I like the sound of your setup

[GOOSE]

Would just like to post a big thank you, if I may, to our members who have taken the time and trouble to post their help to axeltaylor.

Gents, your input has been marvellous. Exactly what Fighter Control is all about.

[hregor]

I've been using a Wellbrook ALA1530+ active loop with a rotator on HF for nearly a year now so my previous post was based on experience that may have got a bit clouded with time. To make sure I wasn't talking rubbish I thought I'd do a few comparisons.

The setup here for HF is an AR7030 (for when the going gets really tough) and an AR5000+ with an SDU5600 panoramic display so I can see noise floors and compare signal strengths with some accuracy.

For comparison with the loop I needed a short wire aerial on the end of a long bit of coax. One of my other interests is satcom and some time ago I built a 7 turn helical aerial for 255MHz. Normally this is connected to a preamp and then to the receiver via 40 metres of coax.

I removed the preamp and connected the coax direct. The result is 10 metres of copper pipe wound like a spring, which is the aerial, connected to the radio by 40 metres of UR58 which is 50 ohms or 40 metres of 75 ohm sat tv coax, I tried both.

The aerial sits on the ground pointing at one of the Sicral sats, so there's no great heights involved and the aerial itself isn't very long. There's a picture in this thread viewtopic.php?f=13&t=36885" onclick="window.open(this.href);return false; . The earth is the circular aluminium groundplane which would have no effect at HF.

Tuning around the usual suspects, RAF Volmet on 5450 and 11253 and Shannon Volmet on 5505, 8957 and 13264 I compared the strength of the signals above the noise floor between both aerials. In each case the loop was only marginally better. It was the same story with those funny Russian CW beacons on 16330.5.

A quick check with my AR8000. not the best HF receiver, at either end of the coax showed no measurable loss of signal and no difference between 50 and 75 ohms.

At 1400z Australia Volmet on 6676 popped up out of the noise on the loop but was barely detectable on the helical.

So what does this prove? I think it proves that HF signals can be received on very simple, low aerials provided they are sited in a quiet place. Getting from that quiet place to your receiver can be easily achieved using ordinary coax. Fortunately if you can't find a quiet site for your aerial, all is not lost because the Wellbrook works very well in a noisy environment, but at a cost.

I used to have a G3... amateur licence a long time ago and worked a lot of HF. For transmitting. all the warnings about matching, resonance, ATU's. aerial height etc are vitally important but I think are not needed for what we're trying to do and only make receiving HF seem more complicated than it actually is. If that puts people off it would be a pity.

Just one last thought, we're not pushing lots of amps of RF up these aerials so we can get away with using very thin wire which is almost invisible.

Roger
PS Thanks Goose, no problem.

[wave scanner]

Not wishing to confuse matters but it is my belief, that height isn't a key issue for receive only antenna's, as long as the antenna isn't touching or
in the immediate vicinity of either large metal or electromagnetic items.
Just keep experimenting with your setup until you reach your optimum.
Also reception is dictated by various other weather & space weather phenoms.. one minute you can hear Hams in the pacific the next you struggle to get RAF Volmet on 5450!
Good luck and be patient

[RichC]

HF comms are no longer busy. I used to stay up at night and between say, 2100 to 0200 about 5-10 years ago i used to be able to fill up 3-4 sheets of A4 paper in logs, mainly USAF. And that was only with 10 presets and manually putting in the others (my fingers used to go like there was no tomorrow on the keypad).
Now, you will struggle to fill up half a sheet.
It's all now secure SATCOM.... with HF as a backup.

[big john]

HI Axel
Here are few to get you started, from my Sony 7600 although I haven't listened to them for a few years.

All frequencies are in kHz, and transmissions use USB

Shore-to-ship, Ship-to-shore
8734 , 8210
13134, 12287
13170, 12323
17326, 16444
17359, 16477
22720, 22024
22723, 22027
22744, 22048
22786, 22090

sorry for the dodgy layout but this forum deletes spaces

[wave scanner]

There is a fair bit of noise around tonight, The Volmets are a good test, As one of Rich's posts suggests i.e NY & Gander 10.051, RAF volmet 5450 & Shanwick volmet 5.505. Also try NAT's 2.891, 2.899, 5.598. 5.616, 5649, etc. 8.906 NY good luck. I like to monitor through headphones maybe a suggestion?