ATAS 120A & LITTLE TARHEEL 2 Antennas: How much of a compromise?

[@aerofart]

GREAT TEST! Concise and useful information with great visuals, audio and production value. Please keep the videos coming. I watch a LOT of YT videos, and I must say Yours is one of the best channels out there IMHO. You know ham radio, and your presentation is better than most “pro” productions.

[@tomcruiser2407]

Hello Tim, that was a great comparison. According to the textbook, that's how it should be, but I was still amazed at how good the small antenna on the car was. There was one component that I was still interested in, and that was the human component. If you just said Ant 1 and Ant 2, for example, that might have produced something interesting.

[@timg5tm941]

Good point..

[@nickgriffithsm0ccg247]

Really good insight Tim - as an ATAS user, in the right conditions have spoke. To VK no issue on 20, however if parked stationary and space allows it’s worth getting the long wire or slidewinder out I feel. Even slidewinder on car with its whip works well - the convenience of not getting in and out the car when it is throwing it down to change bands though is great with the ATAS!

[@timg5tm941]

Absolutely! It’s convenient for sure

[@timdbl7804]

A tip worth trying? On the lower bands, I tend to offset the position, of the mobile antenna, towards the back of the roof of the car; then I guess it is the car which is doing most of the radiating, rather than the tiny loaded whip......and probably radiating much more than the whip.

[@timg5tm941]

@@timdbl7804 yep becomes a tad directional too I would’ve thought

[@G5STU]

Good solid work there Tim, thanks for putting the effort in, very interesting.

[@timg5tm941]

Thank you Stu! I enjoyed the process if not the weather on the night!

[@IZ0MTW]

Hi Tim, appreciate your test and effort in bringing some precise statistics and results. I’d like to point out something though. Uncertainty of reports from the other operator on RX test due to personal interpretation and fading on the signal. An antenna is a passive element of the chain, so what you get in you get equally out. Ie you can’t have difference between TX and RX. The difference , when present, comes from the variation in time. Saying 1S-units equal 6dB can’t be correct. S-meters from our rigs are far from being that precise and linear! Plus they are different from radio to radio. I invite you to test the meter with a sig gen in 1dB steps, you’ll be surprised. Yaesu modern radios for example have (ABOUT) 10dB of difference between S1 and S5 (2.5dB per S-unit) which rise to 3 dB/S between 5 and 9. Almost no radio has a 6dB/S calibration, not even high end ones. Remembering that saying 6dB difference might not seem too much but in effect is 4 times the power! Ie one could lower the power to 25w on the quarter-wave and be equal to the short antenna at 100W. In summery I’d suggest an A/B comparison on a qso done barely above the noise level to well appreciate the difference between the two setups(if the noise level is the same!). Also careful sometimes when the signal pops up, that is not real signal peak (I’ve noticed this on WWV). Mines are just suggestions on data interpretation. Keep the good work and enjoyment! 73 Diego

[@ae1tpa92gwtom2]

Nice experiment and with low noise floor for easy rx results as well, cheers Tim great as always, oh n gd DX of course!!!

[@gtretroworld]

Interesting video there Tim, it just shows you although there was a difference it probably wasn’t that huge especially when you can just plonk that on your car roof and your done. You can also cheat a little on the roof with the radiation angles as that can sometimes be worth a S Point by just moving it about.

[@timg5tm941]

Good point

[@joekrepps]

Excellent, as always! Regarding your thoughts on something like the ATAS-120A on the higher frequencies, I’ve had some emails with Andy, HB9CVQ who’s done some research on mobile HF antennas (check his QRZ page for more). He agreed that the ATAS is sufficient for 14MHz and higher. Personally, with the 891/ATAS combo, on 20m-10m, in a little over 2.5 years of occasional driving, I’m 77/100 towards Mobile DXCC, running 5-50 watts (more than 100 is pointless for me). Last week I set a new distance record for my setup with Seychelles at ~8,600 miles/13.8k kilometers, on 10m. Mind, I’ve often wondered if I could do a little better with a 102” CB whip. 73! WB3CFN/m

[@timg5tm941]

There’s always room for experimentation 👍👍

[@Bilko-M1GSX]

Im starting to do a bit more car hf work Tim so this test is very useful mate. Ive been using a drive over pole support with a 10m sota pole and a 20m end fed. It seems to work okay but its a bit cumbersome. Thx for the vid mate

[@timg5tm941]

My pleasure Ian you sounded good on vhf yesterday on Callum’s stream 73

[@Bilko-M1GSX]

@@timg5tm941 Cheers mate, yes I enjoyed a few hours on 2m, love the 145 events they are always good fun 👍

[@paulsengupta971]

I didn't manage to get up and out on Sunday (I was in Screwfix Live and just caught the last hour of 145-Alive) so I had go do from home. I think I spoke to four people, one of whom lives just down the road from me - though strangely, I spoke to someone near Brighton and one near Crowborough...I know there's a gap in the downs at Guildford, there must be another one somewhere!

[@conorturton]

The advantage the Little Tarheel has over the ATAS is the ability to attach longer whips to it. Stick a decent 6ft whip from a CB antenna onto a Little Tarheel and you'll get around 6dB gain over stock.

[@timg5tm941]

Agree

[@M0RMY]

Also the ability to have it tune while mobile.

[@paulsengupta971]

My thoughts are similar to a couple of the other comments here - do you think it would be a useful exercise to map the stations you heard or spoke to, and compare their location to the difference in antennas? My thoughts are 1) Take-off angle. With the stronger stations being similar in strength, were they the closest ones, i.e. with a higher take-off angle? 2) Was there a difference in azimuth? I was always under the impression that the best signals would be in the direction of the most metal on the car, so with the antenna in the centre of the roof, maybe the signals are biased front and rear?

[@timg5tm941]

All useful observations thanks Paul

[@paulsengupta971]

Another comment, I was very pleasantly surprised when I first bought a 20m hamstick, I thought it wasn't going to be great, but actually it exceeded my expectations. It's certainly a quick way to get up on high ground and start operating on HF. Though I suppose extending a full size telescopic whip on top of the car isn't that slow, assuming it isn't windy or you have a triple mag mount!

[@M7BCN]

Awesome video Tim. I love the Antenna comparisons exercises. Thanks mate.

[@timg5tm941]

Thanks Brian!

[@aerofart]

Did you account for the losses in the different lengths/types of coax running to each of the antennas?

[@martinvanek5951]

I'd be interested in a test of the smaller antenna using 1 or 2 tuned elevated radials. Thanks for the video.

[@KK6USYHamRadioAdventures]

Nice test Tim, I have a HiQ screw driver type but it has a coils about 4-5" around . I should do a comparison of that and a 1/4 wave.

[@timg5tm941]

Go for it Chuck!

[@davidhaman4642]

This not a comparison of atas and tarheel but I appreciate it

[@mw0lge]

very interesting. Somewhat of an investment, but a couple of wsprlite from sotabeams running at the same time would be a brilliant concurrent test of the two.

[@timg5tm941]

Good idea 👍👏

[@mw0lge]

I noticed they are out of stock right now, so not sure if they are discontinued or waiting for a new batch. Home brew versions with a couple of raspberry pi and a bit of filtering, would be a cool experiment and project.

[@MM0OPXFieldRadio]

@@mw0lge Discontinued I believe Richie. I think Zactek is the way to go now. More expensive but multiband with BPF's etc.

[@mattdixon5299]

Fantastic little experiment there Tim with the use of that switch. Out of curiosity, how do you feel they perform vs the trust ampro 20m whip? Is there much improvement?

[@timg5tm941]

I think the Ampro is longer .. longer usually means a little more efficiency with mobile whips Matt 👍

[@mattdixon5299]

@@timg5tm941 yes I figured that, but sometimes the cheap price makes you think otherwise! Haha!

[@4X4-RADIO]

Interesting... One of the Key differences will be Take Off Angle The Full Size Vertical will have a Lower Take Off Angle than the Shorter Loaded Antenna

[@M0RMY]

Don't tell Peter.

[@MM0OPXFieldRadio]

Great one mate. I wonder if the distances were overlayed how it would look? The hypothesis being that the gap would widen the further the QSO distance, or would it? fascinating stuff.

[@timg5tm941]

Very good idea Colin!

[@YO2EOC]

Nice work Tim! On your side indeed no difference, but on my side it was about 2S units. By the way I have my 891 setup according to one of your videos. 73! Eugen.

[@timg5tm941]

@@YO2EOC thank you Eugen and a pleasure to work you 73

[@johnnorth9355]

Your results sound what I would expect with good/fair band conditions. With poor conditions I would expect the 1/4 wave to stretch the lead considerably. Rather you braving the elements than me Tim 🙂. 73 M7BLC

[@timg5tm941]

Thanks John!

[@garyh8315]

A great experiment Tim, the 1/4 wave is putting all those 'bananas' out there, whereas the coil is nibbling at them, preventing them from going out. When will you be trying out the 480? 73

[@timg5tm941]

Soon!!

[@101blog]

A goood wee demo TIm as usual it depends on what you have to hand

[@timg5tm941]

Totally agree!

[@vk2io]

Interesting video with a very confusing title as neither the ATAS nor Tarheel are tested. Should mention Mad Dog Coil loaded antenna versus full-size quarter wave comparison. I fully expect the ATAS 120A to be a long way down compared to the Mad Dog Coil with the same radiator length. Scope for another video comparing loading coil losses with the same short radiator. Personally, I always use up to a 5.6m radiator with my Mad Dog Coil and it has revolutionised my WWFF activating.

[@timg5tm941]

Thanks for the suggestions. The tarheel and atas references were made to alert viewers that this antenna basically mimicked those in terms of size and design. 73

[@Pioneer936]

Nice to see a quarter wave vertical with radials, think if the mobile antenna was directly drilled through roof you would see a big improvement probably match the other antenna

[@timg5tm941]

Hmmm I’m not too sure. I think the fact it’s 5 times smaller than the 1/4 wave beats everything. There would be a slight improvement but I wouldn’t say a whole lot to close much of the gap. 73

[@Pioneer936]

@@timg5tm941 it be worth a test ,there is ohmic loss through a magmount ,lb cebik, walt maxwell, and tom w8ji have all wrote about antenna length not being too much of an issue if fed and mounted correctly, they reckon an antenna can be around 25% of its natural length before radiation patterns become an issue

[@Pioneer936]

@@timg5tm941 ground plane plays a big part in a mobile instalation especially the connection to it

[@paulsengupta971]

@@Pioneer936 With a mag mount, there's capacitive coupling, and a single mag mount should be good for 20m and up. It may need a bit more assistance on 40m and 80m.

[@PaulTaylor1]

​@@paulsengupta971yep definitely the lower bands will benefit from an earthing strap to the car body. Having said that - don't forget that both of these types of antennas can be mounted on a tripod with proper radials. Just because they offer the convenience of car roof mounting, doesn't mean you can't use them in other ways when the opportunity allows.

[@robduncan599]

Isn't the ballpark every time you half the power you lose 3db ? Dito every time you compromise to 1/2 size the ant you lose 3db ? So to go from 5m full size ¼ wave to half 2.5 metres that's 3db then to go to half that again that's another 3db so that is 6db straight of the bat ? On modern rig that is about 1.5 to 2 S units? So it all computes .

[@ErikBijland]

Nice vid! , i like this kind of experiments .. !

[@timg5tm941]

@@ErikBijland thank you!

[@DXCommanderHQ]

Lovely Stuff 🤣👍 (at your suggestion!)

[@timg5tm941]

Ta!!

[@adyg6ad73]

Is it me or do different antennas have different sound? This RF stuff is magic.

[@timg5tm941]

@@adyg6ad73 it’s as if we inject something to help us compare?

[@davidpatrick1813]

Thanx