Many thanks to Barry (KU3X) for sharing the following guest post originally posted on his website:
Product Review: PAC-12 Portable Multi Band Vertical Antenna
by Barry G. Kery, KU3X
I am always on the hunt for a better mouse trap. Dave, NB3R came across a great multi band vertical antenna for portable operating. It’s a, “ PAC-12 7-50MHz Shortwave Antenna “ found on AliExpress.com.
The PAC-12 antenna is designed to operate on any frequency from 6 meters down to 40 meters.
Numerous manufactures make multi band vertical antennas designed to be used for portable operating. Some have quality issues and others may have performance issues, or both? Any hunk of wire or aluminum will radiate if RF is applied to it, but how much will be radiated is the question.
When it comes to ground mounted vertical antennas, one major factor that effects performance is the ground radial field. The PAC-12 comes with a long ribbon cable that you will have to separate each wire and cut to a quarter wave length per band of operation. There are ten wires within the ribbon cable. The length of the ribbon cable is 18 feet. This is too short for 40 meters but perfect for 20 meters. I made four 35 foot long radials out of some wire I had laying around the shack. This will increase the performance on the 40 meter band as well as making a better match. Spread the radial wires out equally around the base of the antenna. Since the radials are not elevated, they do not have to be tuned but it does make for a better match.
The antenna comes with a short stake that can be driven into the ground for attaching the ground radial crimp on to and attaching the feed insulator.
The stake is strong enough to support the entire antenna, even on windy days. The feed insulator has an SO-239 for connecting your coax. The feed insulator must be attached to the ground stake correctly. Make sure the writing on the insulator is on top of the SO-239 and the black portion of the insulator is attached to the ground stake.
So what makes this antenna perform better than most other commercially made portable vertical antennas? Answer, “the mast!”
Most manufactures, not all, use a tapped base loading coil to make the antenna resonant on numerous bands. On a quarter wave antenna, the wire or aluminum closest to the feed point of the antenna is the current portion of the antenna and the current portion does the most radiating.
By base loading the antenna you loose the most important part of the antenna which directly effects the efficiency of the antenna. The PAC-12 has a 4 foot mast that goes between the feed point of the antenna and the tapped loading coil. Each section of the mast is one foot long. The threads on each end are metric, 10 mm.
The tapped loading coil is super easy to use when it comes to changing bands. There is a square contact slider on the bar used to change bands.
The contact slider is very easy to slide up and down, by hand, for changing bands. Look closely at the fourth turn on the coil from the left hand side of the assembly. It is colored brown. That shows you where the tap is to be place to operate on 20 meter. Looking at the right hand side of the coil you will see, around 10 turns from the end another wire is colored brown. This shows where to place the contact slider for 40 meters. We found these two tapes to be spot on. For thirty meters, the contact slider is placed close to the center of the coil. If you want to operate on 17 meters, move the contact slider to the very top of the coil and then shorted the telescopic whip around eight inches. Keep retracting the telescopic whip to raise the operating frequency.
The overall length of the antenna fully assembled is 13 feet. Dave and I tried his antenna on four bands. We were able to get a low SWR on all four bands.
The PAC-12 is advertised to handle up to 100 watts. The quality of this antenna is far superior compared to most of the commercial antennas that I’ve seen that are made in the USA. Most, not all.
DX Engineering sells this product for around $209. Dave purchased his off of AliExpress. I ordered one for myself off of AliExpress and I paid $125 with free shipping. It took two weeks for it to arrive. Search AliExpress, “ PAC-12” and you will see numerous sellers. Prices range anywhere from $114 to around $138.
Just a note on ground radials:
When radials are laying on the ground, they don’t have to be tuned. You should try to cut them fairly close to one quarter wavelength, but it’s not critical. You want to lay down as may radials as possible for maximum performance. But if you can only lay down maybe two per band, the antenna will match and work well. To increase the performance of a vertical using radials laying on the ground, you need to double the amount of radials. This will improve you signal by 3 db. Want an additional gain of 3 db, again double the amount of radials. Once you have 120 radials laying on the ground, you have reached a point of diminishing returns.
A different way of improving the performance of this antenna is to elevate the radials. When doing so, the radials must be tuned to the proper quarter wavelength per band. If you erect four tuned radials on the band of operation, you have pretty much come close to maximum performance.
I appreciate the review Barry! I’ve looked at both the PAC-12 and the Buddistick. I’m still pondering whether I really need a portable vertical antenna. I’ve not used my Super Antenna in years.
Mostly, I’m into wires, especially for the field. Each of my radios is paired with it’s own… My KX2 has the Packtenna random wire or a simple speakerwire doublet. My QCX Mini(s) use a end-fed λ/2, and so on.
Wires just seem more my style. And with that, I guess I have my answer. Thanks again & 72!
de W7UDT (dit dit)
I have been using this same antenna for a couple of years and it has become my goto portable antenna. It is great for travel.
What I like about it is that it packs up really small into the supplied case and performance is quite good, surprisingly even on 40m. I can easily fit the case into a backpack or a bicycle pannier. You can deploy this antenna in < 5 minutes. I am a long-time Buddipole owner/user and I can say without a doubt that the quality of materials and construction of this antenna is comparable.
I determined the 30m tap location between the already marked 20m and 40m taps and marked it with a red sharpie so I can locate it quickly. There is also a much longer whip available for this antenna on Aliexpress. This extends the length of the antenna to over 20 feet and improves performance on the lower bands and also allows operation on 60m. I spent an hour or two with the longer whip and my antenna analyzer and marked corresponding taps on the coil for 60m/40m/30m with a blue sharpie. (Red taps for supplied whip and Blue taps for longer whip). The optional longer whip is over 17 feet long and can be used by itself (i.e. no arms or coil) for operation on 20m through 6m.
A few useful tips. Take the time to figure out and write down the tap and whip settings for your setup for each band using an antenna analyzer. You only need to do this once and it really speeds up band changes. I also pack along an old screwdriver (fits in the case) to make a pilot hole for the ground stake. This makes it a lot easier to get the stake in dry ground. I also broke the radials into two sets of 5 instead of one set of 10. I find that it is much easier to deploy 5 radials at a time as there is less tangling. Generally speaking you want your radials to be at least 1/8 wave on the lowest band of operation. There is no need to "tune" radials on the ground.
The only downside of this antenna is that the threading is all metric (M10-1.5) so forget using any existing 3/8-24 mobile antenna bits to extend or mount this antenna. This is actually quite close to 3/8 inch in size so existing antenna brackets/tripod mounts that accept a 3/8 inch mount can be modified to work by replacing the 3/8 stud mount with a M10-1.5 bolt. One other thing worth noting is that the threading is somewhat coarser than 3/8-24 so when making adjustments ensure that everything is still tight so you don't get wonky SWR readings. My experience is that if a joint is a bit loose it is actually quite loose.
This is a great product at a very reasonable price, I highly recommend it, especially as a travel antenna !
P.S. I bought mine from DX Canada.
I found this antenna several years ago when I was waiting for Pacific Antennas – QRPkits.com – to restock. They have been temporarily out of stock of their PAC-12 antenna for quite a few years. And I left QRPkits.com. Found the instructions on how to build a PAC-12 antenna during my continued google searches, when I found this antenna on ebay or someplace like that. I have one, and have used it as one of my antennas for portable work. Just used it this past Saturday on a POTA activation, along with a few other antennas. I likes the ribbon cable idea, so have added radials to it, put lugs on a group of five wires for easy attachment. I had 22 radials out (that was how many there were in the cable) from 33′ to 15′. I only worked 40 and 20, but did make 21 QSOs of my 73 using this antenna, QRP. I also have a Wolf River Coils antenna, which is similar in operation, Buddistick, pole, hex and a few EFHW and random wire wire antennas. This PAC-12 works well, considering it is a small vertical. I was happily surprised at the quality of the construction. I am happy to know that it is at AliExpress. I have looked at making a similar antenna. When I get the, oh, I will probably never get the shop together to turn the rods. Thanks for the review
I found the same antenna at Chelegance, $114.99.
I am piecing one together. The coil arrived today and four extension rods are on the way. I already have the whip. I can jury-rig a base (or a variety of bases) using a table clamp from a desk lamp and a ground stake.
As with most others, this would likely be a secondary antenna when: 1) traveling. 2) doing a quick activation, and 3) I am sure the bands are open. For travel, it’s a no-brainer, though I would likely also carry a 20m wire and a transformer anyway. For quick activations, the bands would have to be open. Whatever time I’d save with the quick deployment would be given back with reduced performance. I tried that yesterday with a drive-by (in the rain) using my mobile antenna. The bands were open in the morning, but slammed shut shortly afterward. I finally gave up and threw a 10m wire in a tree to get my successful activation. Brutal!
I have one of these — also bought from DXCanada. It has served me well as a portable setup for times when I can’t or don’t want to string up a wire in a tree. On my first day of operating HF (ever) I was able to make a bunch of contacts across the US from southern Ontario, with 20 W.