Best antenna for HF

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luca_t
Posts: 4
Joined: Mon Apr 06, 2020 8:41 am

Best antenna for HF

Post by luca_t » Sat Feb 13, 2021 10:36 pm

I would like to buy an antenna that I can use for DXing primarily on the HF bands and VHF up to 130 MHz but I cannot decide between the Airspy YouLoop and the Moonraker WhizzWhip. The difference in price is quite big although the WhizzWhip is tunable which may improve reception. Would I need a low noise amplifier or an upconverter to use them with the RTL-SDR?. I will primarily use the antenna indoors although I can mount it outside temporarily if required.

snn47
Posts: 247
Joined: Tue Dec 27, 2016 11:00 pm

Re: Best antenna for HF

Post by snn47 » Sun Feb 14, 2021 5:45 am

In short: There is no antenna that provides you good reception, especially at HF with this dimensions, because you can't beat physics!
You can receive with everything, starting from a wet noodel cooked in salt water, a 1 ft nail for VHF and a few meter of wire for HF. If it conducts it will receive. How much signal you will receive, what is the antenna pattern in the direction of the signal and therefore how good reception will be, on the antenna design and to a very large degree on the dimensions in relation to the wavelength.
Any whip is more or less somewhat circulare in reception, meaning all directions, while LF/MF/HF Möbius Receive Antenna (Airspy YouLoop)is directional, meaning it the antenna pattern is not directed toward the signal source signal strength of the received signal will be much lower.

I looked for information on the Moonraker whip, which is advertised not only as receive, but also as transmit antenna. This makes me cautious and reminds me of snake oil you pay for the hope that you can beat physics, nothing else.

Reception between RX: 0.6-500 MHz (500 m to 0.6m) or of change in wavelength of 1:833 ratio!
and
Transmit TX: 3.5-460 MHz (80m to 0.652 m) still a change ratio 1:123
A Power of 10W Max AM/CW/SSB, which on HF only a small fraction will be radiated on 80 m and most of the power will be turned into heat due to losses.
Most wideband antenna designs will not exceed a 1/8 change ratio, which should give everyone a hint of how good such an antenna can perform at best.

The definition for frequency and wavelength change are
MF is the range of 0.6 to 3 MHz (1000 m wavelength) to 3 MHz (100m)
HF is the range between 3 MHz (100M wavelength) and 30 MHz (10m) while
VHF is the range between 30 MHz and 300 MHz (1m wavelength).

You require about a 1/4 of a wavelength to have a tuned/self-resonant antenna that gives you adequate reception if no obstructions conductive (metal) or otherwise are within a few wavelength to your antenna outdoor.
Indoor reception will decrease further, because of walls, floor and ceiling, and the steel reinforcements, electrical cable, water and heater pipes and so on, which will impair reception further. In short increase in losses by obstructions to make it simple.

With just a telescope whip you have adequate reception above ~100 MHz if you adjust it to be about 1/4 wavelength. The box itself should introduce losses, because the whip is connected via a tapped torroid inside the box, which will produce additional losses, , see fig.2 https://www.radioenthusiast.co.uk/artic ... -antennas/
A whip without a counter poise is incomplete without of 3 to 4 rods of the same wavelength to make it a 1/4 wavelength groundplane to give you somewhat stable conditions.
So for VHF you don’t have to spend that much money, because a whip by it itself does the same better.

On HF it is a acts as a switched coil that will provide you an “electrical extension” of the 1.3 m whip, which will provide some matching between whip and receiver. It will not increase the signal strength received by the whip, but just reduces the losses between whip and receiver to some extend. The problem is in my opinion having a toroid core material that works on such a wide frequency range.
Just having a few meter of wire works to if you connect the ground electrically to the water heater radiator or waterpipe.
The airspy loop will provide you much better reception on HF, whip a whip should work better at VHF. Aggain in my opinion there is no torroid core material that works on such a wide frequency range. For more on a LF/MF/HF Möbius Receive Antenna (Airspy YouLoop) read this Airspy YouLoop LF/MF/HF Möbius Receive Antenna (hamradio.me)

luca_t
Posts: 4
Joined: Mon Apr 06, 2020 8:41 am

Re: Best antenna for HF

Post by luca_t » Sun Feb 14, 2021 12:02 pm

Would an upconverter be required for the YouLoop or would a low noise amplifier like the Ham It Up be enough?

snn47
Posts: 247
Joined: Tue Dec 27, 2016 11:00 pm

Re: Best antenna for HF

Post by snn47 » Sun Feb 14, 2021 12:06 pm

Unless you use direct sampling, yes.

joe36
Posts: 51
Joined: Wed Jul 20, 2016 11:09 pm
Location: Cass co. in. 46994

Re: Best antenna for HF

Post by joe36 » Mon Feb 15, 2021 5:38 am

I am an old ham that has played with just about every antenna made.
The one I would recommend is a magnetic loop. It is very easy to make and can cost next to nothing to make.
It is simply a single loop of wire connected across a variable capacitor. The coil “inductor” and the capacitor make up a resonate circuit. This circuit is then put under lode by a smaller coil of wire “inductor” that connects to the RTL. This will not only act as better small antenna than any listed. It will perform as a band pass filter.
This is a link on youtube on how to build a loop. They are sort of specific in using lr44 coax.
It can be any size conductor but the heavier of the wire the better. L have had great success with 1/4 inch soft copper water tubing. When receive only is desired. You can scrimp an the capacitor. ANY AM radio will have one that can be used. Even the cheap transistor type.

This page has a simple cardboard DIY capacitor suited for receive
https://www.crystalradio.net/beginners3/cap.shtml

This page is the youtube video of a build. Minimal research can have a working antenna DIYed for under a $1 or a very nice one for under $20 you can build a fancier marginally better on receive
with sharper filter characteristics. If you build this antenna you will not go back to anything else.
https://www.google.com/url?sa=t&rct=j&q ... uCECN1bhd6

One the magnetic loop and performance compared to a ½ wave isotropic antenna, “dipole”.
It will not perform near as well in some instances and better in others. If you have a radio that is designed for the ham bands with proper filters, strong station interference is no problem and you have the room then the dipole is superior in all ways. If not then a magnetic loop is superior especially for the 820rtl. The antenna being a resonate circuits. It is “tuned” to the frequency you want rejecting others.
Joe

joe36
Posts: 51
Joined: Wed Jul 20, 2016 11:09 pm
Location: Cass co. in. 46994

Re: Best antenna for HF

Post by joe36 » Wed Feb 17, 2021 11:38 pm

Here is a nice video showing how a magnetic loop antenna acts as a tuned filter.
https://www.youtube.com/watch?v=K3n-XC25HL8

Joe

hotpaw2
Posts: 177
Joined: Sat Jan 14, 2017 11:07 pm
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Re: Best antenna for HF

Post by hotpaw2 » Mon Feb 22, 2021 5:58 pm

Check the noise floor at your antenna location. If you can see a raised noise floor on your SDR's spectrum display when you attach a small loop antenna, then a larger quarter or half wavelength antenna won't really improve your reception. Physics says that not only will a better antenna pick up more signal, but more noise as well, leaving you at the same S/N. Plus a small antenna is easier to turn indoors to get better directionality or null out interference.

If you want better reception, you may need to improve your antenna's location, a rural mountain top or something.

VE3EAR
Posts: 49
Joined: Sat Oct 05, 2019 10:13 pm

Re: Best antenna for HF

Post by VE3EAR » Wed Feb 24, 2021 2:32 pm

For coverage from LF thru to HF, my recommendation is the PA0RDT Mini Whip:

https://deimert.se/miniwhip/pa0rdt-Mini-Whip-Manual.pdf

For VHF omni, a simple 1/4 wave ground plane is easy to build and works well.

73, Bruce, VE3EAR

luca_t
Posts: 4
Joined: Mon Apr 06, 2020 8:41 am

Re: Best antenna for HF

Post by luca_t » Mon Mar 01, 2021 8:10 am

In the end I bought an Airspy YouLoop and a HF low noise amplifier. Performance isn't great on the RTL-SDR with a lot of FM interference when the amplifier is on, however my XHDATA D-808 works great with the YouLoop, picking up signals with much less noise compared to its built-in 65cm whip.

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