Superyagi Slim-Jim Antenna for Civil Airband (128mhz Centre Frequency) .
You may recall a review I did quite a while ago on the superyagi j-pole antenna for civil airband.
That first review and a little more info about the business is linked below,
That variant was certainly made to last and that particular model has been used over the last few months mounted in my loft space. No fuss, It just does the job.
To cut a long story very short, about 6 months ago now I had a close look at the owners website and I had a few ideas based around existing superyagi designs, I asked Kevin if could he make these but tailored specifically for the airband listener.
The J-pole I bought a while back was basically an amateur radio j-pole antenna for the 144-146 mhz band but the constructor had kindly made a few adjustments that I had asked for . I am very happy with it but as ever there is always small margin, and I mean small for improvements/enhancements .
I gave Kevin some feedback (all good) and a few more ideas.
The J-Pole was living in the loft space/attic no problems, that is until Christmas was approaching..We have quite a few Christmas decorations and other stuff and we store it up in the loft. So during the completion of some loft antenna “sea trials” I moved the antenna around to different positions moving boxes around at the same time to gain access to new locations. In doing so
The aluminium ferrule joint must have been rubbing away against the wooden purlin it was resting against and the securing screw pan head must have caught against the purlin at some point..
This made one of the two stainless securing screws lose its bite slightly against the threaded wall of the ferrule. Its all good as there are 2 screws anyway but not as good as it was when I received it.
My fault totally, not a fault in construction at all.
Anyway I fed this news back to Kevin and knowing that us airband listeners have a fair share of “loft mounters”.. I had an idea for future design consideration.”Could you strengthen the ferrule more perhaps” ?
Kev said “probably..Good idea, Ill have a go”…
A surprise parcel duly arrived , before Christmas I might add, but it was only this week end of February I managed to get some spare time to see what Superyagi creations were enclosed within.
First up we have a Slim Jim antenna centred for 128mhz civil airband, for the wider sections, very similar diameter and grade of tubing used in the standard J-Pole version i reviewed last year.
There are a lot of similarities in the materials used but quite a few differences as well, in the main these are in and around the spigot/ tube ferrules.
The Slim-Jim does not offer any noticeable gain over the standard J-Pole, both are more or less identical as regards to performance but I could see advantages and disadvantages to both types depending on an individual listeners setup/station .
The superyagi slim jim centred for 128mhz civil airband is pictured below as delivered straight out of the box.
Assembly is complete in just a few minutes, here is a photo of the antenna completed and some rough dimensions and features.
There is a small gap in the tube with a glass fibre spigot support about 1/3 of the way up one side, this is an important feature of the Slim Jim design.
Another pic, 1.73m long overall, the U shape of the U is around 80mm wide.
First impressions are, much better for loft mounting due to the increased rigidity. This isnt going to flinch even if I hit it accidentally.
The U shape at the top lends itself to an easy DIY cord or string hanging point.
Screw a cup hook into the timber apex or beam and you are good to go providing you have around 1.75m of height to play with up there.
Of course this inst the best way of mounting any antenna. Outside is best and Kevin has kitted out the mounting bar with a pair of stainless steel U bolts that will take a 1 1/2 inch (38mm) mast. Like the J-pole If you mount it properly with good quality brackets, sleeve anchors fixed into brick not mortar and a decent wall thickness mast, this isnt going anywhere even in the highest of wind gusts.
Some excellent guidance on poles/masts and brackets from Justin an aerial installer from Yorkshire,UK linked below
Now on to some bespoke enhacements/improvements and I specifically mentioned the sleeves and spigots.
Here is a close up picture of the all aluminium sleeve “Joint A”, it is not shown complete as both parts slide together fully so that the spigot support is no longer visible.Then the screw is tightened to secure.
Next up, Another view of the same joint showing the increased wall thickness on both parts of the antenna.
An interference fit of two short tubes to construct a coupling,and with the original element tubing that makes 3 layers on each side, this is a very tight and secure way of mating. This provides 50% or more wall thickness (and thread) so there is only a need for 1 screw not 2 as on the J-Pole.
Now on to the other side “Joint B”, this is the area that features a deliberate/by design gap in the tubing.
Heres the female ferrule, thats had the same triple wall treatment.
Heres the fibreglass peg which is non conductive of course to create the gap but still provide strength, its riveted into the aluminium tube.
And here is that joint (Joint B) fully assembled showing the gap of about 1 inch between the tubes.
Okay with the antenna fully assembled lets have a look around at the workmanship and hardware.
The “business end”, here we find the SO-239 coaxial connector, stainless steel u bolts and the green tube clamps for the aluminium tube elements.
A word on those clamps later. One more small seemingly insignificant thing ..The logo sticker I like that a lot !
Simple but effective message, It conveys a sense of quality, Made in Great Britain and the guy who made it is proud of the product and his company name, That’ll do for me..Nothing wrong with being proud if you make nice stuff.
The U bolts are very heavy duty, think of your TV antenna U-bolt and multiply x3 on the thickness at least, very robust.
Heres the reverse side, some weather proofing /anti corrosion sealing varnish for the solder on the SO-239, Stailness Nylok self locking nuts holding the clamps to the base plate..
Oh yes, the green tube clamps which are Stauff GR2 types. Well if you shop around you will find these between £5 and £15 each depending on how many you buy.
Here you get a pair of those for a start, a PTFE SO-239, about 2.5 mtrs of aircraft grade aluminium tube, some thick “ally” plate, a pair of heavy duty zinc plated U bolts and a sprinkling of A2 stainless fasteners. All that and the specialist tools skill to bend tube and put all this together.
Thinking Doing it yourself ? You would be out of pocket if you constructed to this standard..
Buying one of these is a no brainer, it will serve you well for many years of civil airband listening.
A quick sample of reception from my fabulous new toy, an Airspy R2 software defined radio receiver linked up to the Superyagi Slim Jim Antenna.
“AF115Q / Air France 115 Quebec” gets a little confused for a moment or two trying to find the VOR way point Honiley (HON) which is a few miles south of Birmingham UK. Following the short pause the flight deck realise they have been past that one many times..Following this ATC at London Control start to get busy with the rest of the traffic on the scope. Crank up the volume and click bottom right of the window below for full screen mode, here comes a 30 second burst of Airspy R2 audio magic, enjoy.
(Still cant believe the stuff this little box of electronics can do !)
There is a Military airband version of this slim jim antenna and the J-pole antenna which are tuned for 300mhz centre frequency. These are much smaller in the overall length dimension.
Take a look at Superyagi Antennas ebay shop and message seller if not in stock, Kevin will make you one up for around £45, a bargain.
or enquire directly via his website
Superyagi Dual Band J-Pole for Civil and Military Airband (128mhz/300mhz)
Yes another Superyagi variant of the J-Pole, this one is special in so much as it covers both civil and mil air bands.
The best of both worlds perhaps.
This one I found to be more suitable for outdoor mounting, I dont know why perhaps I am paranoid about this one getting knocked about as it is wider than the single band j-pole to accommodate the additional tube mount. It may be happy mounted in a loft if you have plenty of space but keep all these antennas away from metal water tanks and such like as this will effect the reception performance.
Also I thought of the possible difficulties with hanging this one up in the rafters and getting it to sit nicely balanced and straight.
No doubt I will find some sort of workaround, or I could just go for mounting it outside next to my 2m/70cm amateur radio white stick.
Here is the 128/300mhz dual bander straight out of the box. I have put some dimensions on there.
The 63.5cm tube is very heavy duty , this slides into the longer 1.15m tube and the whole lot is mated together with a very strong ferrule and secured with a pan head machine screw.
The other shorter tubes are mounted on to the base plate. Again initial assembly was completed in a few minutes, the threads are different for each tube and they only fit on to the base plate in the correct order so its very easy.
When the antenna is fully assembled, it looks like this
Here is a closeup photo of that longer section, its made up of the 1.15m tube and the 63.5cm one, they slide into each other.
Note the wall thickness of the larger ferrule and also the smaller insert tube.
Remember if outside this part may be under high stress due to gusting winds.
This element on inferior versions would normally be the Achilles heel or weak point either at the join or at the point where it is fitted to the base plate.
Triple wall interference fit on the female…Top quality here, and no mistake.
Here is the other /base plate end of that element.
2 rivets to secure a huge threaded aluminium strengthening spigot ,about 70mm long in fact.
Also an interference fit I think.
Now to the base plate itself, some dimensions and a closer view
A single heavy duty stainless steel pole/mast clamp.
Now the underside
All dimensions in photo above are in mm.
The so-239 coaxial connection is on the far left.
The 56.5cm tube has a very tight solid aluminium insert which is turned on a lathe to produce a 3/8 male connection to the adaptor on the base plate.
I havent tried this one linked up to a radio yet, but it looks very promising.
I will have to link this up to my amazing Airspy R2 SDR radio and give it a try.
Around £50 I think, expensive ? For the many hours of happy listening you will get its peanuts.
I know the military airband guys will like the idea if this perched on their roof for when they are stuck at home with no airfield away days to go out spotting.
There is another dual band j-pole model by another manufacturer, that is for amateur radio use and that model has stainless steel whips which will sway all over the place in high winds altering the tx/rx performance significantly.
Superyagi is a small cottage business and like a few others past and present I could mention in the UK radio game like Purvisell Ltd, RFComms, Jaycee Electronics and Flightdeck they really do care about their products and customer satisfaction.
This is great to see.
Im glad Kevin took my feedback on board and met my challenge of reinforcing those joints.
The difference is a marked improvement on which was a very robust original design.
The only further minor enhancement (if you could call it that) I thought of was to supply a few grub screws along with the pan head screw with all antennas that feature spigots so that a user had a choice which to use for his/her installation situation. I would wager “the loft mounters” would go with the grub screw every time to avoid snagging against obstructions . A2 grubs are pence each, just a thought.
My favourite out of the 3 models is the civil airband slim-jim featured at the top of this article, personal choice not a performance based selection.
I see the J-pole and J-pole dual bander being popular for outdoor installs, light , low wind resistance.
The slim-jim I see being a firm favourite of the “attic dwellers” amongst us in the airband fraternity and the much shorter military model (around 75cm overall I think) may be well suited to being mounted on a short pvc pipe spike shoved into the ground next to the car for those who park up next to guarded mesh fences frequently…Yes I know you crazy milair fans spend hours there. Guys who spot from the car will find the performance spot on.
Thanks to Kevin @ Superyagi Antennas for the loan / experimental prototype models to try out.
Would you like to try making your own civil or military airband antenna ?
If so, check out this link to another page in my blog.