Hi all, was wondering what you all feel would be more efficient for the 20-6 meter bands, a low band Motorola whip (like CHP used to use and SFPD still use) with Icom AH4 or a screwdriver antenna like the Hi Sierra or other screwdriver?
I know a screwdriver is nice to be able to be exactly tuned but it would look stupid on the side of my car. I'm mainly on 17 and 20 meters.
Thanks all
Jennifer
What antenna is more efficient for hi bands HF.
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What antenna is more efficient for hi bands HF.
Jennifer Bond
"There is no greater, darker, deafening sound than, after the loss of a K-9 partner, climbing back into a patrol car and hearing only silence."
"There is no greater, darker, deafening sound than, after the loss of a K-9 partner, climbing back into a patrol car and hearing only silence."
In reference to this as well as your post in the Equipment forum, you might want to talk to kc7gr. I think he has a lowband ball mount whip antenna (very much like CHP and SFPD lowband) hooked up to an antenna tuner on his van.
Ham Radio Outlet sells Hustler brand ball mounts and springs, not sure where you'd get the actual whip though.
Ham Radio Outlet sells Hustler brand ball mounts and springs, not sure where you'd get the actual whip though.
Re: What antenna is more efficient for hi bands HF.
A "rule of thumb" for frequencies lower than about 50 mhz-- antennas that look good are usually only good for looks, even if great pains are taken with their installation. You are going to need an "ugly" antenna if you expect to have more than a peanut whistle signal.jjbond wrote:... but it would look stupid on the side of my car. I'm mainly on 17 and 20 meters....
Be careful about using a standard ball mount with a tuner. The insulator will flashover due to the substatially higher voltage in that application as opposed to a coax feed to a tuned whip.
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Tom in D.C.
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HF Mobile Antenna Choices...
An antenna tuner makes the radio see a 50-ohm load but how much of that gets radiated is always a big question. The radiation resistance of the SYSTEM may be 50 ohms, but the tuner doesn't do any radiating work for you.
If I had to work 20M mobile I would probably opt for one of the motor-tuned antennas, ugly though they may be, because I'd know that the radio is looking at a 50-ohm ANTENNA load when tuned to resonance, and I would probably not be using a tuner in the system. Of course a quarter wave is inferior to a half wave radiator but that's the basic limitation of HF mobile work no matter how you slice it.
If I had to work 20M mobile I would probably opt for one of the motor-tuned antennas, ugly though they may be, because I'd know that the radio is looking at a 50-ohm ANTENNA load when tuned to resonance, and I would probably not be using a tuner in the system. Of course a quarter wave is inferior to a half wave radiator but that's the basic limitation of HF mobile work no matter how you slice it.
Tom in D.C.
In 1920, the U.S. Post Office Department ruled
that children may not be sent by parcel post.
In 1920, the U.S. Post Office Department ruled
that children may not be sent by parcel post.
There is no question that a well designed screwdriver-type antenna will outperform just about any other type of mobile wide-band antenna system. Unfortunately they are necessarily big and ugly.
I don't use one, but only because I need very rapid tuning for ALE purposes. If I could get by with the slow tuning that is inherant with a screwdriver-type, I would definitely be using one.
The most important thing with a mobile HF antenna is to get the base of the antenna as high as possible. This means that a shorter antenna will probably work better than a long antenna for the same overall height, because the base of the shorter antenna will be higher up the vehicle.
For example, I have my tuner/antenna combination mounted on the roofrack of my Landrover. The antenna is a helically wound whip about 3.5 foot long. Overall height is about 10 foot from the ground. Other Landrovers with 9 foot whips mounted on the fender about 2.5 foot above the ground have an overall height of 11.5 foot, but don't radiate anywhere near as well as mine. There's also the inherent mechanical problems with a long flexible whip. For HF work, the 9 foot whip really is a problem.
Most of the professional HF manufacturers (Codan, Barrett, Motorola) have opted for a pretty good compromise of a tuner/shortened stiff whip combination that is designed to mount on the front bumber of the vehicle. This gets much of it away from the bulk of the vehicle body so that it can do it's job properly.
Regards,
Marc - ZS6HZ
I don't use one, but only because I need very rapid tuning for ALE purposes. If I could get by with the slow tuning that is inherant with a screwdriver-type, I would definitely be using one.
The most important thing with a mobile HF antenna is to get the base of the antenna as high as possible. This means that a shorter antenna will probably work better than a long antenna for the same overall height, because the base of the shorter antenna will be higher up the vehicle.
For example, I have my tuner/antenna combination mounted on the roofrack of my Landrover. The antenna is a helically wound whip about 3.5 foot long. Overall height is about 10 foot from the ground. Other Landrovers with 9 foot whips mounted on the fender about 2.5 foot above the ground have an overall height of 11.5 foot, but don't radiate anywhere near as well as mine. There's also the inherent mechanical problems with a long flexible whip. For HF work, the 9 foot whip really is a problem.
Most of the professional HF manufacturers (Codan, Barrett, Motorola) have opted for a pretty good compromise of a tuner/shortened stiff whip combination that is designed to mount on the front bumber of the vehicle. This gets much of it away from the bulk of the vehicle body so that it can do it's job properly.
Regards,
Marc - ZS6HZ