Portable “Antenna’s”

Since I got the Xiegu G90 I have been playing around with building suitable antennae for other bands such as 20 and 40m. I was pleased with the results of the coax end fed antenna I build for 10 and 11 so knocked up something similar for 20m. Initially I tried just putting a choke round a ferrite core at the 1/2 wave mark but the analyzer was showing things were way out of whack so removed it and wound an electrical quarter wave of coax around an 8″ plastic core.  Instantly showed an SWR low around 13.5mhz and 3 or 4 goes of removing a couple of inches of coax from the top of the coil had an SWR of 1.17 at 14.2mhz. But I had a problem. My 10m pole was not really long enough to keep the coil off the ground! It was difficult to set this antenna up vertically due to the length. At this point I decided it would not work for me and went to work on the 40m dipole. This was also long but a few times of fold the wire back on itself, test, if OK snip off the tail, test again, fold back, test, snip, test…etc etc soon had an SWR of 1.3 : 1  at 7150. Feed point up about 9.5m and ends at 3m off the ground. Easily covered the entire 40m band under 2:1. I am sure if I was to raise the antenna further; and efficiencies improved the SWR curve would be much sharper. For the amount of wire and work to get a resonant 40m antenna in the air this has to be the easiest yet. The wire was plastic coated and quite light but for portable use it should be OK. Not something you want to put up as a “set and forget” antenna by any means. No balun. Just direct feed to coax. Portable. 20w max. Just needs to work. I think I will make something similar for 20m. Simple is always good when out in the woods. And Inverted V’s do work well and they don’t have to be heavy.  For a single pole set up I think an inverted V is the simplest, cheapest and possibly most efficient antenna one can make for portable use. It is resonant on one band and that should be the band you are working on.

Join the 40m wires together and could be forced into use on 20m as a quad!

When it stops raining I will be going portable on 40m.

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XIEGU G90 SDR

xiegu front panel

This little radio is causing a few waves around the world and it is not hard to see why. It is the complete portable set we have all been waiting for and it does work rather well. It has all you need to head off into the hills with a piece of wire and a battery and get on the air. It receives well and the 20w PEP output on SSB will get you heard.

There is a lot going on with this radio but it doesn’t take long to sort out the things that are useful. Changing the frequency, mode and band are all off buttons either on the front of the radio or on top. The buttons are small and don’t convey a lot of feeling. I have read a lot of complaints about the buttons not working well. In my experience you must not press the buttons too long Just a press and back off. Hold them too long and they do nothing. They are not back lit or easy to read so best try to remember where they are!

What don’t I like about it? Not a lot and they are mainly minor. Its a tad heavier than it could be. The DC line seems a little flimsy and the buttons take some getting used to. But once you do get this thing on air it plain works.

I was hunting about for the DNR but it doesn’t seem to have any. Didn’t stop the signals coming in. Filters could be narrowed but the passband doesn’t shift. The mic compressor did not seem to work. Big deal. No RF gain control, just an attenuator and a preamp. It didn’t stop the radio from doing the job it was intended to do which was to transmit and receive signals.

The Tuner works on just about everything. Power is adjustable from 1 to 20 w in 1 watt increments. The fact it puts out 20w carrier in AM and 20w on SSB would indicate it is not being stressed on Sideband. It receives very well. Signals just pop out of the noise. The display shows a lot of whats going on and Ver 1.7 of the firmware also decodes CW. This radio came with Ver 1.6 of the firmware and I have not got around to updating it. too busy having fun!

The head is removable. The connecting cable is in the box along with the cable to update the firmware. I really can’t see me remoting the head because the cable sticks out the back and would make it difficult to stick on to a dash board or whatever. Someone is going to have to come up with a bracket to hold the head securely somewhere using the screw holes on the head that secure it to the body. It also needs a bail to hold the radio at a better viewing angle when in use. The speaker is on top but I think most people would want to use headphones in the field. A lot of the functions are also available on the microphone if your fingers don’t suit the buttons on the radio. Mic cable is a straight ethernet RJ45 cable. I am hunting around for a flat cable to replace the stock to reduce the flexing of the RJ45 socket on the set. There are also RJ45 right angle adapters that would work well to keep the mic cord from sticking out at 90 degrees.xiegu mic

I am not going to go into how to do this or that, but I do feel the majority of users will find this radio to be very friendly to use and it works surprisingly well. I don’t know what improvements the makers will make via software updates but it will certainly be interesting to see what the future will bring.

The mod to get it to TX from 0.5 to 30mhz is out on the net. Didn’t take too long. Hopefully Xiegu will not counteract it in software in later updates.

Bottom line is that this is a great little radio which will continue to get better with every update. It can only get better!

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Programming 10m ‘CB’ Radios

What an oxymoron this title is! You can’t have a 10m CB radio! Either it is a Ham radio or CB radio. Supposedly. What I mean by this is a radio that covers the 10m band but retains it’s origins as a CB radio by doing it it bands of 40 channels. ie most export CB’s. Except the Optima and maybe a few of the earlier sets which are no longer produced. The fact that almost all of the ‘export’ radios we can buy these days are programmed in bands of 40 channels really pisses me off. Why not 100 channels? Why 10khz steps. None of them step in 5khzs, (except the Optima). But the Anytone SSB 10m radios, and the maxlogs  allow us to define what is actually in the bands themselves. That opens up a few opportunities.

Like what?
Well..lets take the AT-6666 as an example. Out of the box it covers 10m only. Plug in the programming cable and run the program on your connected PC and we can opt for the full coverage mode of 25.6-30mhz, spread over a bunch of 40 channel bands. The program also gives us the ability to decide what frequencies we want to have in those bands. For example; many New Zealanders still want to have access to the old 26mhz CB band. No problem, just go ahead and input 26.330 into Channel 1 of band A and keep on going till you have all the 40 channels written up then upload it to the radio. Turn it on and you have the NZ 40 in band one ready to go. Awesome..and 60 watts of PEP to drive it with. The AT-6666 should be available ex stock NZ in a couple of weeks for around US$250.

Lets face it..the 2 bands in 25mhz are useless (anybody use 25mhz?)  so I would put NZ 40 in band A and the US 40 channels in Band B. That brings us to the wonderful freeband, that area between 27.410 and about 27.855. Bands C and D get entered with every frequency from 27410 on up with 5khz steps. Forget about the channels up here as they are pretty meaningless anyway. look at the frequency on the radio. Alpha channels in order!
Band E. Input the CB Marine frequencies and any other specialized frequencies you may have.
Band F,G,H,I and J. Start at the beginning of the 10 meter band and input the entire band in 5khz steps and whatever of the 10m FM segment suits you. But the AT 6666 radios can’t do split. There was one radio I remember having to input TX and RX frequencies into. Forget which one. All these radios will step in 1khz steps if set to do so but default to 10khz or what has been programmed in the band.

The Lincoln 2+ does do Split TX and RX but we can’t input frequencies for the individual bands. (Yet.) The lincoln 2 is an Anytone design and I suspect build. Its made in China. The Mckinley’s and Grant 2 are made in Vietnam and to my knowledge we have no means to mess with the Grant 2 and Mckinley with a PC and programming.  I doubt if that will change.

So if you want to get your NZ frequencies and increased power with a new SSB CB radio you better get an Anytone.

NZDAT

The Anytone AT-6666 and the lincoln 2 and the Stryker 955 seem to share a common architecture despite looking totally different outside.

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President Grant Expanded Mode

president Grant 2 Premium

Once the Grant 2 Premium is Expanded several functions are added to the radio which are not covered in the Manual. Despite an upgraded mother board there has not been much change in the way the radio works, but here is what I have found so far.

  1. The frequency coverage is increased from 25.615 to just over 30mhz in 10 bands of 40 channels. To scroll thru the bands repeated press’s of the F button. Bands are identified on the screen from A thru J.
    A is the normal 40 channels and B is the freeband. A bit clunky. As you change the band the last frequency you were on in that band will be displayed.
    If you are going to be doing a lot of navigating with this radio I recommend using the memories, the programming of which is in the manual so I won’t cover it here.
  2. The Power is increased to around 20w SSB/FM and 8 AM depending on tune.
  3. Up 10kc.  To access the Alpha channels a long press of the Mic Gain button jumps the frequency up 10khz and the ‘mhz’ wording on bottom right of display will blink repeatedly. Another long press reverts back to standard. The frequency will change accordingly but no change to the channel numbers.
  4. Minus 5 Khz A long press of the MEM button will drop 5khz and the frequency will track the change. No other notification so keep your eyes on the frequency display! Both the changes in 2 and 3 remain in effect until disabled by pressing the appropriate button again. Turning off the radio does not cancel the function.
  5. UK CB Channels. The UK CB channels can be accessed from the mode button. keep pressing the mode button from AM to FM to USB to LSB and the next press gets you into the UK FM CB Channels. Cool if you live in the UK I guess. President Grant 2 PPresident 2 prem UK

The Grant 2 Premium is still a CB, but a glorified CB. Great little CB actually. I think you might find it a little restrictive to work in the 10m band as you can only work frequencies ending in 5 and 0. It has 5 memories which can ease the navigating niggles of 10 presses of the F button. I prefer the green to the orange display colour but everyone is different. Not much not to like. The extra power and heatsink are worthwhile additions.

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Portable and More

I have been working with the 300 ohm TV ribbon to make several antennas and have come to realize that while it is nice and light, the lack of any semblance of strength once the plastic jacket is removed does not make it very suitable for repeated deployments. it is also difficult to remove the plastic coating without losing some wires in the process. I resorted to using a soldering iron to remove the plastic while keeping the thin copper strands intact. I would be really pissed off after walking several hours to a chosen location and find the antenna of my dreams had fallen apart on me after a few minutes of use. Another problem of using ribbon for the feed was to obtain consistent results re SWR and the need of a balun at the end. Ribbon is probably great in a fixed location but problematical when you are operating from a variety places and you may not be aware of where and how you are going to have to run the feed to the radio. Despite the weight of coax my thoughts are drifting back to coax.

Luckily we had a couple of fine days recently one of which was windless so I was able to play around a bit more with the Bi Square. By trimming the twin feed I was able to bring the SWR down to about 1.5 with the 450 ohm ribbon which was much easier to trim than the 300 ohm TV stuff. I kept trimming till I noticed the SWR on channel 1 started to creep up. Need to measure what length I ended up with. I was unable to test the results on air unfortunately, as no one about. But I now have an antenna I can transmit with. I probably have gone about this the wrong way and need to make sure the loop is resonant before playing with the feeder. I also note in the books that the tuned feeder is a stub and shorted at the bottom and the matching points found by trial and error, which is a bit hard with the plastic coated feeders I have on hand. Where does the balun go? Also the books state the Bi Square should be 1/4 wave above ground at the feed point which I am unable to achieve with my 31′ pole. While I am a firm believer in getting as much wire in the air as possible, I think I have to rethink the bisquare. The added wire also adds to the windage and deployment hassles. I like it and it certainly warrants further work, but I will put it on the back burner for now till I get an antenna analyser to bring the loop into resonance before working on the feed system.
Another thing is the wire. I need to be using hard drawn non stretchy proper antenna wire and not the weak stretchy flexible thin stranded normal wire with heavy insulation that is readily available in the shops here. Buying a ready made wire antenna is probably quite worth it, as to build something that will last will cost you! However the purpose here is to work out what works for me first, and then make it properly!

BI Square pictures
20190819_111024[1]20190819_112140[1]20190819_112151[1]20190819_112155[1]

So where to from here.?

What works well so far? The conventional inverted V. And the recently completed 1/2 wave coaxial vertical. I like the vertical. Easy to deploy. Doesn’t need guys and coax all the way to the radio means consistent results in the field.

Which brings me to the conventional single quad loop. Can be fed with  a quarter wave of 75 ohm coax back to 50 ohm coax to the radio. A bit of gain, bi directional, closed loop, and can get the feed up to approx 1/2 wavelength so a little bit more out of the way.
Lots of  information on making and feeding quad loops on the internet.
Diamond shaped.
That’s the next project. I think it could be used vertically without too much hassle running the coax feed down one of the guy lines that pulls the loop away from the pole.

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The Coax Vertical Sorted

coax dipoleWe have continued to play around with the Coax cable vertical antenna and I think it is sorted. I still need to do a lot more on air tests to make sure it does work significantly better than the Wilson 5000 but we seem to have tamed the RF currents that were on the braid and causing the SWR to rise as power was increased. It took about 10 turns around a toroid choke (ferrite FT240-43) placed 1/4 wave in free space below the Coax coils.  The SWR stayed constant as we increased the power from 4 watts, to 10 watts and then 50 watts on AM. No problem for the RG 58/C cable I have used.  I only had a 40 ch radio to check the bandwidth Channel one was 1.2 and Channel 40 was 1.4 so we could fine tune things further but I will sit on this for a while. Looks like we should get a MHz under 1.5:1 which would suit me fine. Easiest way to fine tune this antenna is just to wind the air coil up or down an inch or two. I don’t want to cut the radiator just yet. Covering the NZ truckies on 26.450 AM can’t be a bad thing. Most active part of the band around these parts it seems.

The picture below is basically what we built. An end fed 1/2 wave antenna I am told. Works like a dipole for gain and take off angles which is not that bad.  I saw on the net that Sirio also market a similar antenna in a fibreglass stick called the gainmaster HW.
https://www.sirioantenne.it/en/products/hf/gain-master-hw
The picture in the manual sure looks the same! I think mine is easier to carry around as long as you have either a fibreglass pole to stick it up in the air or something to hang it off. Sirrio probably use better coax as well…hope so ..to justify the cost. And someone in Germany has also come out with something that sounds the same but without any real pictures and dimensions one can’t be sure. There is one thing for sure: It ain’t magic. Its easy to build yourself. Just one bit of soldering; the plug on the end of the coax.

The only crucial part is the coil. It seems to depend more on the length of coax cable in the air coil than the number of turns or the diameter. 5 or 6 close spaced wraps around 5 or 6 inch diameter will get you close. The rest just falls into place. I started with 2.65m of radiator and the same from where the braid is cut to the top of the coil. First tune by moving the coil up or down and find how it is changing the SWR. Follow it to get around 1.2 to 1 on the frequency of choice. The SWR was fine on 5 w carrier but rose as the power was increased. If I added or removed wraps on the air coil the SWR increased so I added a toroid choke 1/4 wave in air below the coil and ‘voila’ flat SWR under power!!

coax vertical

It fits my needs for an easy to deploy vertical antenna. The 30′ pole stays up with out guying in a moderate breeze. It can take a few hundred watts with ease. Now I just need to prove it radiates significantly better than the Wilson. One thing for sure. When the wind is blowing, its cold and it is pissing down with rain I will be snug in the car with the wilson no matter what!
Initial transmit testing does not show much difference with signals of 5 or more on the Wilson. On the receive I am seeing 2  to 3 S points on the meter. The big difference on ground wave is when the signals are weak or low. Then it does lift the signals out of the noise. It should do. It is about 6m higher in the air so hardly a fair test! Have not had any chance to test it with Skip as the skip has been dead of late.

The Coax ‘Cobra’ laying out on the ground
coax cobra

radiator

The coils
the coils

The Toroid
toroid

For those interested here is what I did to build this antenna.

Parts: 15m of RG58/C coaxial cable. (Non foam, Non aluminium shield), One PL259 Plug, tape measure, yellow insulating tape, scissors.

Work out the dimensions from the formula 300/fx (mhz) x .94 for wavelength of the wire.
((300/27.3) x.94)/4 for a quarter wave.  For 27.3mhz it came to 2.582, which I rounded up to 2.65 meters to give me some wriggle room.

Measure down 2.65m and place a wrap of yellow tape under the 2.65 mark. (Tape 1)The top of the tape should be 2.65. Cut off the black polythene jacket to expose the braid and remove the black plastic without messing up the braid underneath. You will end up with 2.65m of braid showing.

Pull the braid down and over the black plastic outer. Bunch it up and it slides over OK.
When it is all pulled down the center conductor in its solid plastic jacket will be exposed. All 2.65m of it. Now carefully cut the braid at the yellow mark. Use sharp pointed scissors. You don’t want to snip or cut into the plastic inner or it will weaken the antenna.

Now you will have the braid over the coax and free to move. Slide it down towards the bottom and tape it in place temporarily so it doesn’t move around. We can use the braid as a sleeve later on so best leave it on the coax.

Next. Measure 2.65m down from the top of the yellow tape under the white conductor you have just exposed and wrap a turn of yellow tape. (call this tape 2) This will be the top of the turns of the air coil. For no good reason other than to complicate matters I decided I would use an electrical quarter wave of coax in the coil. I used 2.65 x 0.66 (the velocity factor of the this coax is around 66%. That gave me 1.75m.

Measure down 1.75m from Tape 2 and wrap another yellow tape around this mark (Tape 3) So now we have 3 wraps of yellow tape on our coax. The first one is under the exposed inner conductor, the second is 2.65m down from that on the black shield and the third is 1.75 meters down from there or 4.40m down tape 1.

Coil up the 1.75m of coax below tape 2 around a 6 or 7 inch former. Has to be neat and in line. No cross overs.

The braid. After soldering the plug to the coax I stretched the braid down the outer and soldered it to the outside or ground of plug. I think this should probably be 1/4 wave in air but the braid wasn’t long enough so I just used it as it was. End up with about 2 meters or so. It made a difference at lower power levels so I left it on. (Lowered the SWR) If it works for you cover it in heatshrink. It only connects at the plug.

That’s about it. If you are going to use 100w or so you could add the toroid as pictured above and can probably dispense with the braid. I placed the toroid a quarter wave or 2.65m under the coil and wound it guanella style, in one side and out the other.
http://www.vk3bq.com/2014/09/24/11-current-balun/
https://www.iz2uuf.net/wp/index.php/2017/05/09/dont-wind-chokes-on-red-toroids/

I just tape the antenna to the pole every 75 cm or so as I push it up to prevent it flapping about. The antenna radiating part is everything above the coil.  (Fingers crossed!)

How to tune.
3 things can be altered to affect the tune. The length of the radiator (exposed white inner core) and the length of the black outer above the air coil. (and the coil itself) First work out where it is at resonance..Should be resonating lower in frequency using these figures and wind the coil up to shorten the bottom section. 1 or 2 inches at a time to start with to see which way the SWR is changing. You can add to the coil or subtract a turn as well to get a feel for things. The swr will change as you change the height above ground so try to take the swr readings at the final height if possible. Last thing is to cut or bend the top radiator to bring the SWR down to around 1.2 or so across the 40ch. Actually anything 1.5 : 1 across the band is good.

Basically : if your dimensions are in the ballpark you just need to play around with the coil to change the swr. It is quite reactive and any metal objects nearby can cause the swr to change. Just rearrange coil to suit!

Have Fun!

Appreciate any feed back.

 

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The Coax Vertical Antenna

coax dipole

The coax half wave antenna under test on Mt Egmont. I have now been playing around with a half wave of coax cable to find something that works for me. The criteria was quite simple. It has to work considerably better than my wilson 5000 on the car, be relatively simple to erect, vertically polarized for local contacts, strong enough to take the stresses of multiple deployments, easy to stow in the car and  and give consistent results.

I have the advantage of owning several 10m fibreglass push up poles which are light and are only a meter and a bit long when scoped down. Pull up a section and give it a twist and it will stay in place quite well. For semi permanent installations just tape up the joints. These work great. You can get them from Spider beam up to 20m expanded length. (http://www.dj0ip.de/spiderbeam/fiberglass-spiderpole/)
Make sure you get fibreglass and not graphite as the graphite is conductive enough to affect any antenna close to it.

When I first began looking into this antenna I was thinking “dipole”, and a few of the designs I looked at depicted the coax cable with a quarter wave of the braid folded back down over the black outer and the exposed quarter wave of center conductor as the radiator. That at least looked like a dipole. Coax up to the center and two halves radiating. Perfect. It is in a fact a sleeve dipole according to the books. The first problem with this design on 11m was that the amount of braid removed to expose the 1/4 wave inner radiator did not come close to 1/4 wave when folded back over the black outer. No worries: add some more; which I did. Didn’t work worth a shit. With a quarter wave radiator and a quarter wave below it, fed in the center you would think it would work in some fashion, but the SWR was over three to one so I knew I had work to do. I looked back at some of the sleeve designs and most of them were for VHF where the size of the sleeve was a smaller ratio to frequency than at HF. And it seemed the sleeve was not a radiating part but some sort of matching device and was not supposed to radiate and was an electrical wavelength. Bugger. This was starting to get complicated. I recall I had seen a design for a similar antenna that had a few coils wound at the bottom of the outer coax radiator. By trial and error I got about 5 loops in the coil and by raising and lowering the position of the coil I could get the SWR to start coming down to around 1.6 : 1. It did not seem that the sleeve or folded back braid was doing anything. Other than the less braid the better it worked. In the end I cut all the braid off and left the coils which was the design I had seen years ago. And Voila! SWR 1.3:1. But what is it? Is it a quarter wave or an end fed half wave? Does it work? It does work. It gets out a bit better than the Wilson but the big difference is in the receive on low signals. It certainly hears a lot better. In local line of sight contacts it did not make much difference with strong signals, but really helped pull low signals out of the mud. I still have not put more than 80 watts into yet but that will be the next test. Need to know we can put 3 or 4 hundred watts into it without things messing up. The SWR rises a little when changing from 15 to 80 watts, so we still have some extra choking to do. But where? At the set or under the air coil at the bottom of the radiator?

So where do we stand? It is easy to erect, it works but I think it could be better yet, it is robust and packs down to nothing. Once you get the coil set, it works the same each time, but the swr does change a little with height and it did rise when it got rained on.

I have some 2.25″ ferrite cores so I will wind the coax around one in various places and see what gives. Might also add a 1/4 wave counterpoise to the end of the lead in coax just to see. My gut feeling is we still have radiation in the coax which may or may not be helping the SWR and or radiation pattern.

Its working and we are making contacts.

I have built a second one and it works pretty much the same. Just got to get the right length of coax in the coil and get it positioned to get the lowest SWR.

Next I will work on the folded dipole from TV ribbon. At the moment it plugs in to a 4:1 balun and has a flat SWR of 1.5 across the 40ch. I am happy with that but have had not much chance to sit and play on it. I have seen a design which uses all 300 ohm ribbon and has a stub soldered in line with the feeder. I don’t think I can bring the ribbon into the car without messing the balancing things up so need to get back to some coax at some point. Advantage of the wire antenna is that tying off the inverted V ends stabilizes the pole somewhat, but it takes a lot longer to get it in the air and pull it down and it takes up more real estate and more obvious.

And then there is the bisquare. Need to see what matching they used in the CB handbook by Bill Orr. Its old but it will probably still work!

The Baluns are in.

IMG-20190810-WA0006

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