XIEGU JPC-12 Vertical Antenna Instructions
- June 9, 2024
- XIEGU
Table of Contents
XIEGU JPC-12 Vertical Antenna
must confess to being more than a little confused when the latest portable
antenna arrived for review, direct from China. The legend on the small zip
around, compact,
‘handbag’ sported the embroidered legend of JPC-7. The antenna inside was in
fact the JPC-12 a ground mounted, 100W maximum vertical. The confusion didn’t
stop there, the component parts looked to be too small to provide a decent
sized, meaningful antenna and only weighed around 1.4kg in total. To add to
the confusion the foreign language handbook wasn’t in Mandarin or Cantonese
…not that I can read either. I discovered later with the help of a friend,
that it was written in basic every day keyboard Chinese.
Translation efforts proved very limited, as my friend from Hong Kong doesn’t
understand any technical terms. The handbook is cunningly designed for more
than one model of antenna. It’s difficult when you don’t understand Chinese
and don’t understand that to read about either of the two models, you simply
turn the book over and start reading from the other end.
If All Else Fails …
Despite my maxim ‘If all else fails read the handbook’, it was relatively
simple to assemble the antenna without it. I was staggered to discover that
from small beginnings it turned out to be twice my height, quite impressive.
Just for fun I later timed the assembly from opening the bag, planting the
antenna and plugging in the coaxial cable (not included). My record was 4 mins
26 seconds, against the handbook quote of 3 minutes. Resonating and matching
certainly takes more time. I’ve experienced many mobile and compact antennas
over the years and way back reviewed the original Buddipole, when it was still
available as an online DIY project. The concept of this antenna is much like
the single-ended Bud-Stick that was produced later. Mast sections of the
standard Buddipole are 55cm each and their Mini version reduced to 28cm. This
compares to the JPC masts at 35cm. Looking through the package I recalled my
basic physics and the sage advice of the Old Timers of my boyhood radio club.
Experience has taught me that the junction of dissimilar metals is not a good
idea unless you’re deliberately looking to create a high resistance or a diode
effect. Such things weather badly and must be kept very clean. This antenna
uses 10mm studding bolts and brass alloy threaded sockets. There’s plated
stainless, plated steel, manganese steel, aluminium and more. Engineering
wise, the metal parts are of a good standard and fit together extremely well
on the flush faces Of course, it’s a portable antenna and realistically
unsuitable for anything other than a temporary setup as it stands. Never throw
it back in its bag and forget it, when it’s been out in the wonderful wet
British weather.
From the Ground Up
Starting from the ground up literally, the 25cm earth spike is curiously light
in weight, but of course this is a portable antenna so weight or lack of it,
is important. Part of it isn’t electroplated so as to give better contact with
the ground. I quickly realized not to hammer it into the ground to prevent
damaging the exposed thread.
Perhaps a flush socket design as against an ex-posed thread would have been
better. I discovered the best way to achieve a reasonable result was to attach
the base-connector unit and/or the first of the four anodized alloy tubes and
push down hard. Alternatively, to use a rubber tent peg hammer on the socket
end of a tube and not the exposed ground spike thread. It’s worth noting for
those like me that enjoy mixing and matching various antenna parts from
different systems, in the vain hope of achieving the ‘holy grail’ of compact
antennas, that this antenna is not compatible with others. It uses 
QRP on the Yorkshire Wolds. 
JPC-12 outdoors. 
Coil close up. 
ARRL Antenna Handbook 1964 (Reproduced by kind permission of
ARRL, copyright retained.) a 10mm thread system and not the ubiquitous
American, 3/8th UNC threaded antenna parts and mounts we came to know in the
CB boom. However, if you want to make up other mounts or play around, 10mm
threaded bar and bolts are common fare at the local DIY emporiums. A mirror
mount type bracket or G clamp with a 10mm bolt spring easily to mind Attaching
the loading coil section is straight-forward, so too is the 2.5m, ten section,
stainless telescopic whip. I was concerned that the combined weight of these
two components at around 280 grams would make the antenna unstable. However,
in round terms it’s balanced out by the weight of the base connector unit that
feels heavy on first handling. I can’t decide whether this is a happy accident
or good design. The complete assembly is reasonably stable and certainly
unobtrusive for a typical campsite. For hill topping, carrying some ground
pegs and para cord is advisable as the coil/whip assembly certainly attracts
some windage. The package includes a single counterpoise made from ten-strand
ribbon cable. It attaches by means of a ring connector between the ground
stake and the base/connector tube. Unlike the thin, separate, spaghetti wires
provided with some other portable antennas, it’s one single strip 2.64m in
length and 1.2cm wide. The hand-book says it’s 10m. Perhaps lost in
translation it actually means it’s a quarter wavelength on the 10m band and
there-fore harmonically related only to the non -WARC bands. That said, when
on the ground the single counterpoise that’s incidentally handling 50% of the
RF, becomes de-tuned anyway. This means its length isn’t that critical. I was
tempted to split the wire but vowed to make more like it for better results.
Attaching more wires with a similar surface area at this point does improve
things and can make matching easier on favourite bands but has not much effect
on expanding the narrow band-width of the system. With a single wire counter-
poise, carry a compass. It can help to point the RF towards a favoured
direction. This proved great for directing my signal to PY on 15 metres, or
was it just that band conditions improved a little bit after I moved the wire,
some-thing to play with?
Note to self: Must make more grey counter-poise wires, not as garish as
other colours or as discreet on a campsite as my green ones and less of a trip
hazard in the early hours!
I was intrigued to know what was in the heavy sealed base unit. Does it
perhaps contain a balun or an UNUN? Metering through showed no sign of a short
circuit and therefore unlikely to contain a balun. I was guessing that it
might contain ferrite rings to tame any RF on the coax feedline, so asked the
question of the manufacturer. The reply came back in Chinese. The non-
technical translation came out as being the presence of “3 metal bars”. From
this I take it that my second guess was correct. Indeed, the coax proved RF
docile under test.
Now for the Loading Coil
They do say there’s nothing new under the sun. Immediately I unpacked it, this
antenna jogged my memory of a DIY design in an old ARRL antenna handbook; back
in the day when everyone made everything. I’ve always meant to build one but
now I don’t need to bother, see Photo 4. Assembled, the coil sits at around
one third of the total antenna length. Accepted wisdom is that it should be
higher at around between 40-60% in order to maximize current distribution. It
would be interesting to see what adding two more threaded tubes would do in
terms of radiation and matching. The translated handbook says that the 33
turn, silver-plated wire loading coil is wound on a Nylon former. The former
is most likely moulded, not 3D printed, but the material makes me think of it.
Unlikely to be pure Nylon because this can absorb water and is not good for
antennas. At 45mm in diameter it’s a good size in terms of maximizing Q factor
and better than some of the competition. An add-on coil with no tapping slider
is said to be available to extend the antenna’s use to 80m, subject to the use
of longer counterpoise wires. Thus far, I haven’t found a stand-alone 80m
inductor available online.
Perhaps I’ll find out in Part 2 of this review (next month). Yes, there’s more
to come from this antenna system…
Mounted on a slider and using modern materials to maximize contact pressure,
matching is achieved by means of a manganese spring steel contact. Longevity
is an unknown quantity at this stage. It looks pretty resilient to me. Kept
clean (with a contact burnisher, not sandpaper!) and with care it should last
a long time. I wonder if you can buy a spare contact. On close inspection, it
looks to be very much an easily replicable item. The loading coil is short-
circuited from the top down, not engaged from the bottom up as I originally
guessed. There’s a silver mark for the 40m band near the top and a lower gold
mark for the 20m band. 40m and 20m markings are guidelines. Instructions say
that on 20m the whip section needs to be reduced by 20cm. Of course, fine
tuning is a movable feast when you factor in each individual portable location
and ground characteristics into the equation. 30m isn’t marked or listed, but
it’s somewhere in between the other tappings. You also have to be careful that
the spring contact only touches a single winding. To help, it’s notched in the
centre. Being a compact antenna on the lower bands, bandwidth is narrow. The
quick way to match it is with one of the new pocket analyzers, but is
achievable by first maximizing a received signal followed with a VSWR meter on
transmit. Good matching is critical.
What I didn’t know until the manufacturers kindly sent me the English version
of the instructions is that for 15m, the coil is removed. The four lower rods
remain and only seven sections of the whip plus 10cm of the next section are
to use for resonance on 15m. For the 10m band, the telescopic antenna is
connected directly to the base alone. It’s
fully extended, less half the top section (fully extended for 11m, methinks).
Reading this was my eureka moment. Of course, it’s simple! From 15m to 6m,
including WARC bands, it becomes a straightforward ground-mounted quarter
wave.
Why didn’t I think of that before?
Matching this antenna changes with every change of location and ground
condition. 1.1:1 or better is achievable on 40m as the specifications state.
That is, given some time fiddling and fine tuning, damp ground and a decent
earth. I’ve also experienced locations where this and anything better was
difficult without the aid of an external tuner Not ideal for QRP where every
watt counts. The manufacturer states that 1:1 is possible from around 30m-6m
but as yet I’ve never quite achieved that across the whole range. The higher
in frequency you go the easier it becomes to find a decent match but I still
go back to the need for additional counterpoises or better earthing to get
good results. That said, from an initial trial as supplied, in a quiet RF
location, clear low angle takes off on G3UNC’s campsite in East Yorkshire; 5
watts of CW produced good contacts all around Europe from Sweden to Spain,
with very little effort on 40m. I prefer to make live contacts with real
people because data hasn’t really floated my boat, as yet. Nevertheless, I do
think that this type of antenna lends itself very well to data contacts and
WSPR, if larger antennas are not practical.
What do I Think of It?
Over time the market for small, compact antennas has grown to offer a range of
options and cost. Several have become costly to make and ship, especially
those using high-end components, and include extras such as optional brackets,
connecters, adapters coax and cases, etc.
From my initial observations and misgivings, I have come to appreciate that
this is a very acceptable and unobtrusive device, particularly for operating
/P just about anywhere, provided you accept its limitations. It has a small
footprint and is reasonably unobtrusive when erected. I really like that it’s
compact and lightweight, takes up surprisingly little space when packed, yet
assembles into a good size at around 12ft, in old money. Weatherproofing is
minimal. To help with this I’ve made use of a £1.50 plastic funnel cut to
provide a friction fit above the coil. For heavy weather, I’m considering up
cycling a plastic drinks bottle with the bottom removed. I just need to find
the right one. I have a few concerns regarding the differing metals but to
some extent it’s unavoidable. As with almost all of these end-fed verticals,
earthing or counterpoise is key to success. Adding three or four radials to
the kit does pay dividends. In the last few months advertising for this range
from China has boomed, online. Traditionally, Chinese products are sold
through agents. It can be a case of ‘caveat emptor’ for the unsuspecting buyer
when dealing remotely. Since receiving this antenna direct, several UK
suppliers have taken it up under different branding. While there may be some
cost difference buying from UK sources, delivery from stock and the knowledge
that reputable dealers support their buyers is well worth it. Price wise at
circa £199.00 in the UK, it stands up well against what else is available.
Overall, I like it and I’m using it. I’m also really looking forward to
reviewing the JPC-7 dipole – Part 2 coming next month! PW
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References
Read User Manual Online (PDF format)
Read User Manual Online (PDF format) >>