Basic antenna questions....

Status
Not open for further replies.

Quebec337

Member
Joined
Jun 3, 2017
Messages
54
Location
Quebec
Ok now, I'm in my infancy in terms of shortwave and receivers, it's even worst when it comes to antenna.

I own an Icom R-9000 (surprising, isn't it :) and would like to have the best antenna possible.

At the present time, I have an approx. a 107 feet simple longwire, nothing more. Should I buy one ? Should I improve mine ? I don't even have an antenna tuner, and not sure what "end fed" really means...

My antenna is kinda 100 feet long and 30 feet high on one side going west, and about 7 feet on the other side on my door, going east. The junction between those two being above my door. So it's some kind of a "T", but disproportionate on the western side.

There is so much technical terms involved that I did not assimilate yet.....I feel lost in a see of infos....help :)

Thanks,
Matt
 

wyShack

Member
Joined
Nov 18, 2008
Messages
436
Location
Campbell County, Wyoming
What do you wan to hear with your radio? That is usually the first question -especially with a radio that covers so much of the spectrum-you will likely want more than one antenna depending on what you are trying to hear. Along with what you are after, where are you and what kind of room do you have. Where you are will let us help you find the 'local' stuff. Knowing if you are in a city or rural will tell us how much 'noise' is around you. And knowing what you have to work with for antennas (house on large lot, tower.apartment or whatever) will help trim down the possibilities.

Welcome to Radio Reference.
 

Quebec337

Member
Joined
Jun 3, 2017
Messages
54
Location
Quebec
Thanks for asking, it's very kind of you.

Well, I live by the riverside, in Quebec city, Canada. I don't think there is much noises around. If we say a big city would be a "10" noise level, and the middle of a forest "0", I guess I could say I'm at "3,5" or "4" at home.

I have more or less 100 feet available (westward, and parallel to the river). On the eastern side of the house, it's a little more complicated (which explains why 90 % of my simple "T" antenna is on the western side). Apart from the wire of the antenna itself (made of half of a speaker wire), there is no component to my antenna (well yes, homemade plastic insulators, made from some of my son's small hockey sticks....hehehe). That's what we call homemade :) But hey, I've put some efforts into it.

My main goal into shortwave listening is to catch those small and barely audible and exotic transmissions (wether it's a radio station, maritime, aeronautical, etc...). I'm very fond of the Pacific region, I should say. I assume I've got the sensitivity and capability with the R-9000 to get there. So now, I'd like to get the most out of an antenna (which I don't think the actual one is giving me). There seems to be a lot of interesting frequencies between 8000 and 9000 Mhz in fact. Anyway.

There's a million questions in my mind.....but basically, the main one would be : what would be the best set up available to get the most out of the sensitivity of the Icom R-9000. I'm a little technicaly lost when it comes to the components of an antenna (Is a tuner a must have ? Could it transform a barely audible signal into a fair one ?)

Of course, I'm more than willing to educate myself, but there is so much to learn and experiment than at this stage, I feel the need to reach for some experienced individuals, voilà :)

Cheers,
Matt
 

wyShack

Member
Joined
Nov 18, 2008
Messages
436
Location
Campbell County, Wyoming
Ok now we are getting somewhere-shortwave reception is dependent on many things and the antenna used is one of them. Lately propagation hasn't been all that great. With that said, learning to use your receiver can help a lot. Check out the VOLMET stations (either on the RR wiki or Google.) These are HF stations that transmit weather information for transcontinental aircraft. While a bit on the boring side, they are all over the world and transmit continuously -making them a great way of finding out what you can hear at any given time.

Now a couple of quick pointers for listening. Listen above 10 Mhz during the day and below that at night (just a rule of thumb-and not cast in stone). Noise level is higher in summer than winter -especially at lower frequencies. Get (or Google) a shortwave schedule for broadcasters.

Antenna- one of the simplest antennas is a dipole- it is just a run of wire with the feed at the midpoint. A dipole is actually best at one frequency where it is resonant. If you are working in Mhz, the length of a dipole is 468/frequency =length in feet or 143/frequency=length in meters. Dipoles are fairly broadband on receive and fairly non directional. I would make one for about 10 Mhz and you will likely be fine from 3- 15 Mhz. A tuner is more needed for transmitting( get your ham license). If an antenna of this size pegs out your S meter due to noise, build a smaller one. Another popular antenna is just a random length of wire (end fed). 40-50 feet will work well for most uses.

Welcome to the hobby and feel free to keep asking questions.
 

chief21

Member
Premium Subscriber
Joined
Mar 2, 2004
Messages
1,366
Location
Summer - Western NC; Winter - Tampa Bay FL
The term "end-fed" is used to describe a certain type of wire antenna. All antennas require two components... an active component and a ground component. In the case of an end-fed antenna, the is only a single wire and the active component (the wire) is connected to one side of the receiver antenna connector while the other side of the connector is connected to the ground.

A typical wire dipole, on the other hand, uses two equal-length wires, with the feed connection in the middle. Each "side" of the antenna is isolated from the other by means of an insulator. The two "sides" of the feed line are connected to the antenna connection of the receiver. You can google the terms "dipole" or "end-fed" to find much more information. In your case, a dipole would probably be preferred for monitoring.

You should also be aware that wire antennas are used primarily to monitor HF signals from very low frequencies up to 30 MHz or so. If you also wish to explore the VHF (30-300 MHz) or UHF (300 MHz - 3 GHz) bands, you will need some totally different antennas. Antennas for these frequencies are usually vertically-oriented, rather than horizontal, and the specific type will depend on your particular interests.

You have a very high-end receiver there. Enjoy your new hobby.

John
 

jwt873

Member
Premium Subscriber
Joined
Dec 1, 2015
Messages
994
Location
Woodlands, MB
The IC-R9000 was high end model in it's day and even by current standards it still is a very high quality receiver. You won't need preselectors or tuners.

You can get by with the random length of wire that you have. (I did for many years as a shortwave listener).

Length isn't as critical for receiving compared to transmitting. For transmit antennas, if you're just an inch out, it can affect the SWR. Not so with receive antennas.

You can purchase commercial short wave antennas. --> https://www.radioworld.ca/alp-dxswl They will provide a bit better coverage since they are 'tuned' for each international shortwave band.

But since they're just wires, you can cut and assemble your own for much less. Plus if you build your own you'll learn as well. Google for "home brew shortwave antennas".

Make sure you connect the Shortwave antenna to the rear antenna jack marked 'HF'

The IC-9000 is also a formidable VHF/UHF scanner... You'll need a special antenna for that.

A good basic antenna that covers a wide range of frequencies is the discone.

Radio World in Canada has a range of them. Here is one example --> https://www.radioworld.ca/mfj-1868

This will connect to the 30 to 300 Mhz Jack on the back of the radio. You can also connect it to the 1000 to 2000 Mhz Jack as well. But in practice, you probably won't hear much there.
 

Quebec337

Member
Joined
Jun 3, 2017
Messages
54
Location
Quebec
Thanks John, that helps a lot !
It's simple and clear.....that's the way I like it.

I already have ideas for antennas.

Let me ask : I already know the formula to calculate the lenght of my antenna, if I do a dipole for a specific frequency. But what about the vertical coax that will go to the receiver, do I have to consider it in my equation ?

I feel the need to ask because the coax will be at least 25 feet from the receiver, and part of it will not be totally...."vertical", I should say ? :)

Matt
 

wyShack

Member
Joined
Nov 18, 2008
Messages
436
Location
Campbell County, Wyoming
Matt-

At those frequencies (HF) and under about 100 feet-for receive I would not consider the coax at all. Remember to ground the radio and use a lightning protector (also tied to you house ground). and enjoy. For general HF listening, I am using a 68 foot wire sloping down a bit form my tower to the top of my garage- it works great although I expect I could do better at the higher frequencies (20 Mhz and up) with a dipole or shorter wire. Receive is quite forgiving as most receivers are almost too sensitive-noise elimination and selectivity are what helps improve reception for the most part.

Again, welcome to the hobby..
 

Quebec337

Member
Joined
Jun 3, 2017
Messages
54
Location
Quebec
I'm surprised, cause most of the diagrams on google image show the coax in the middle.
Ok then so, what would be your type of wire, if I may ask ?

Matt
 

wyShack

Member
Joined
Nov 18, 2008
Messages
436
Location
Campbell County, Wyoming
With a center fed (dipole) you connect the center to one leg and the shield of the coax to the other. An end fed wire just uses the center conductor, or the shield is grounded on both ends. If center fed, just let the cable drop down as much as feasible, then run it to the radio.

With my end fed, I use a transformer between the coax and tie the 'ground' on both sides of the transformer to a 'leg' of my tower, which is grounded via its foundation rebar.
 

Quebec337

Member
Joined
Jun 3, 2017
Messages
54
Location
Quebec
Ok now, here's another :

In a dipole, why do they call each sides ''a quarter of a wavelenght'' ? Shouldn't it be ''half of a wavelenght'' ?

Let's say I'm doing a 46 feet dipole to catch 10000 Mhz.: It will be 23 feet on one side, and the same on the other. But, something cutted in two pieces is a half, not a quarter...so why calling each sides ''a quarter of a wavelenght'' then ?

I know there must be a simple and rational explanation to this one and I'm not honouring myself asking, but hey : I just don't get it :) :)

Matt
 

jonwienke

More Info Coming Soon!
Premium Subscriber
Joined
Jul 18, 2014
Messages
12,138
Location
VA
Each half of a dipole is 1/4-wavelength. Total length is 1/2-wavelength.
 

popnokick

Member
Premium Subscriber
Joined
Mar 21, 2004
Messages
2,088
Location
Northeast PA
There's a lot more help and info for this topic available in another Forum here on RadioReference -
HF / MW / LW Monitoring > Receive Antennas (below 30MHz)
 

slicerwizard

Member
Joined
Sep 19, 2002
Messages
6,648
Location
Toronto, Ontario
I don't see where anyone has explained that your longwire antenna is a high impedance antenna and therefore it should be directly connected to the HF ANT 2 connector, not HF ANT 1.

But are you really running your longwire antenna into your house and all the way to your receiver? That sounds like a good way to pick up noise from all of the electrical devices in your home.
 

jonwienke

More Info Coming Soon!
Premium Subscriber
Joined
Jul 18, 2014
Messages
12,138
Location
VA
OK good, but how come the terminology does not include the total wavelenght then ?
It does. Dipoles assumed to he half-wave unless specified otherwise. Ground plane antennas (essentially a dipole cut in half) are either 1/4-wave or 5/8-wave, but most commonly 1/4-wave.

A 1/4-wave dipole (two 1/8-wave halves) would not resonate properly and would work like crap, so it pretty much doesn't exist.
 

Quebec337

Member
Joined
Jun 3, 2017
Messages
54
Location
Quebec
Good, thanks.
I'll try to make a dipole, for a very specific frequency, just for fun. We'll see.
Cheers,
Matt
 

chief21

Member
Premium Subscriber
Joined
Mar 2, 2004
Messages
1,366
Location
Summer - Western NC; Winter - Tampa Bay FL
Matt -

To clarify your wavelength question, the term "wavelength" refers to the electrical length of a given radio wave. As an example, the wavelength of a 10 MHz signal is approx 97 feet. Therefore, the length of a one-half wavelength and one-quarter wavelength 10 MHz signal is approx 48 feet and 24 feet, respectively.

So a half-wave dipole wire antenna would be constructed with a one-quarter wavelength wire (24') as one side and a separate one-quarter wavelength wire (24') as the other side. The two equal sides are typically separated by an insulator/connector device where the antenna feedline (coax or ladder-line) is connected. The ends of each wire are connected to an insulator, which is then connected to the supporting line (typically nylon cord/parachute cord).

John
 

Quebec337

Member
Joined
Jun 3, 2017
Messages
54
Location
Quebec
Super, thanks John !

I'll be connected with an RCA jack in the back of the receiver. What happens then with the braid of the coax : is it joined with the center of the coax before entering the back of the radio ?

Matt
 
Status
Not open for further replies.
Top