1 Product Overview

The Miracle Antenna QPack Precision Tuner (QPack for short) is a light weight low power antenna tuner suitable for use in backpack, portable and mobile installations. It can also be used as a backup tuner in your shack. The QPack is rated to handle 20 Watts continuous power into balanced or unbalanced loads. The manufacturer claims a matching rage of better than 15:1 and rates the 20 W handling capacity as conservative.

The unit is light weight, I don’t have a scale so I can’t be exact here, but it weighs about as much as a 600 page paperback book. The unit measures 7” long by 3 1/8” wide and is 2” deep. These measurements include all knobs and connectors.

2 Background

Robert Victor, VA2ERY of Miracle Antenna asked to write a review of the QPack unit. In return for my review I will receive my QPack unit at a 50% discount price and receive free shipping. In other words, I’m being paid $89 for this review. I think that it is important for the reader to be aware of this. However, I plan on measuring and evaluating the unit to the best of my abilities as I would any other piece of gear that I use.

2.1 My Qualifications

My radio and electronics background is varied. I have been a ham since 1992 and I have had some formal electrical engineering training as a Computer Engineering student at the University of Utah. I have also worked as an electronics technician and lab assistant at the University of Utah where I had many circuit design, building and electronic measurements jobs. As part of my radio hobby, I have been learning more about electronics design and antenna design. I am very much an amateur in these areas but I am qualified to make measurements and evaluate the performance of the QPack unit from the standpoint of a portable antenna builder and HF operator.

My current radio focus is on the design and construction of efficient and portable HF antennas and man-pack HF radio setups. I also spend my time experimenting with and designing homebrew RF circuits.

Professionally, I am a software architect and I’m responsible for designing and building applications on the Windows platform. I’m also a consultant and I provide training in product life cycle, object oriented programming techniques, software testing and the effective use of the Microsoft .NET technologies.

3 Test Equipment and Procedures

Most of this review will involve using the QPack in various scenarios and reporting on it’s performance. I will also do some controlled measurement and A/B comparisons.

I will be using the following equipment to evaluate the QPack

· MFJ-269 antenna analyzer – Used to measure antenna characteristics and as a transmitter to tune the Qpack to my antennas. I will also use the MFJ as a low level signal source for some crude signal strength & efficiency tests.

· ICOM 756 HF receiver with internal tuner – I will be comparing the QPack to the IC-756 tuner.

· ICOM AH-4 antenna tuner – I will be comparing the QPack to the AH-4 attached to an ICOM 706 MKII/g HF transceiver. I will also use the S-meters in the 756 and 706 for relative signal strength measurements.

· G5RV “short version” – My G5RV is up 30’ and fed with 75’ of 50 Ohm coax cable. The cable contains a choke balun in the form of a 12” diameter coil with 15 turns of coax.

· Vertical antenna test platform – My vertical antenna test platform is a setup I use to build and measure the portable verticals and dipoles I build for field use. I will describe it more below.

4 General Impressions

The QPack is a solid, nicely made unit. The Load and Tune scales are well done and easy to read. You can quickly approximate a setting or count tick marks for a more exact measurement. The labels on the unit are easy to see at all angles and in low light. This is due to their simplicity and high contrast. The manual is short and easy to read and does a good job of explaining how to use the unit.

I took the end plates off my QPack to have a look inside. The internal construction is solid, with clean solder joints and well mounted components. The circuit board is firmly held along it’s entire length by extruded ridges in the aluminum case. The case and end plates are attached by 4 screws on each side and the unit is RF tight. Although the QPack is not waterproof, the well sealed ends, single piece case and oversize knobs should do an excellent job of keeping dust, dirt and minor splashes out of the innards.

All of the knobs and connectors are top quality with a solid feel and they are easy to use with a few minor exceptions. The Load and Tune knobs are large and stiff with a very smooth movement and no backlash. The load and tune controls take a little extra effort to move but in return you get smooth, accurate, reproducible settings that will not be jarred loose in a pack or mobile setup. Despite the effort required to use the tune and load controls its easy to use them one handed by leaning your hand on the unit while turning the knobs with your thumb and forefinger.

Once nice feature of the load and tune knobs is that they work very well for ultra-fine adjustments. I’ve found that with just finger pressure I can make minute adjustments to get the best SWR. If you are into finding the lowest possible SWR then you will like this ability. The lack of backlash is impressive. I hope that as the unit wears in, that the controls will not loosen up.

The BNC connectors are solidly mounted and even when I used 3” worth of adaptors to connect the unit to my test antennas there was no wobble or intermittent connection issues with the connectors.

Session to session repeatability of the QPack was excellent. The best tune position for an antenna and frequency were always within 1-2 tick marks of the previous session. The only band that was worse than this was 6 meters. Even on 6, by starting with the recorded settings a 15-20 second adjustment procedure was all it took to retune. This may very well have been an environmental factor. The issue only occurred with the tree mounted G5RV. My other antennas did not show the same problem.

5 QPack in the Field

In the next section you will see the results of my tuning measurements when using the QPack with my G5RV short dipole and portable vertical. In this section I’m going to focus on my in the field subjective experiences with the unit.

Since Field Day is coming up, I have been spending a lot of time planning and preparing. Part of my preparation is to setup and operate my equipment in field conditions. I made the QPack part of my setup.

For this field test, I used the following equipment:

Icom 706 MKII/g with AH-4 antenna tuner.
33 AH battery.
10’ military whip vertical on a 4’ base.
Transmitter power varied between 5 watts and 25 watts as per the 706 power meter.
I used SSB exclusively for these tests.
The QPack antenna tuner.
Various other stuff.

So that I could test the QPack and do some A/B comparisons, I built another vertical base, attached my backup whip and hooked the antenna up to the QPack. This antenna was identical in all ways to the one that I attached to the AH-4. The antennas were about 10 feet apart.

During my Field Day dry run I worked 40 meters, 20 meters and 6 meters. On 40 & 20, I made contacts in New York, Michigan, Arizona and Washington state. On 6 meters, I worked 2 local hams, one about 50 miles away and the other 2 miles away. (Today, June 19, 6 meters is open! Need more power! I’m hearing mobile stations in CA, AZ and Mexico)

The QPack did an excellent job. During each QSO, I switched between the AH-4 and the QPack. The station at the other end never heard the difference. I did not let them know that I was testing a tuner or antenna. Instead I waited for contacts where the other ham was a bit long winded and switched antennas while they were talking. On the receive end, I did not notice any differences in signal strength once the QPack was tuned.

Of course, the AH-4 tunes automatically and almost instantly. But, since I had recorded my settings for the QPack I did not find tuning to be a chore. A few seconds and I was ready to go. When I started transmitting, I would monitor my SWR meter and make minor adjustments to “tweak” the SWR.

There is one area where the QPack outperformed the AH-4. The AH-4 will often let RF back into the radio via the control lines which causes the radio to lock up. I need to rearrange my ground radials, move the AH-4 or make a choke to fix the problem. With the QPack in place, I did not have any RF feedback issues. Of course, there are no control connections between the QPack and the 706, but so what. RF feedback issues were not a problem when the QPack was inline.

I also had the opportunity to try the QPack with my new Force 12 Sigma 40 vertical dipole. I setup the Force 12 in its 40 meter configuration and left off the hairpin match. I was able to tune up on all bands from 80 meters to 6 meters (and had some luck on 160 meters) using the QPack and the Force 12. I did have some tuning issues. The QPack/Force 12 combination was not as easy to use as my other antennas. The nulls were often very sharp and, except on 40 meters, the standard QPack settings did not always work – instead, I often found myself using oddball settings like setting the QPack band switch to 14 meters when working 40 meters.

Since I have not had any experience with the Force 12 yet, I can’t say why this happened. Still, the combination worked and I did have time to make 2 20 meter contacts, one to Japan and one to Austin Texas. I did not do any A/B comparisons, but the QPack seemed to work fine. My Japan RST was 47/QSB at about 40 watts and my Texas RST was 48 at 10 watts.

Note that I did not notice any heating or other issues with the QPack at 40 watts but I was on the air for only 30 seconds. The unit is not rated for this power level so please don’t try this at home!

After 2 days I have to say that the QPack performed very well. It spent it’s time in the 90 degree sun, sitting in my driveway or in the dirt. I dropped it, kicked it, grabbed it by the antenna wire and used it. I had no problems with it. At the end of the day, a quick wipe with a rag and I stuffed it in my pack for the next session. It held up very well and I’m looking forward to using it with my vertical whip and the Force 12 during field day. Look for me on the air, I’ll be on the HF Pack calling frequency, 18.157.5 on and off throughout the weekend. I’ll also be working 20 and 40 meters, SSB and CW.

I had one minor issue after 2 weekends using the QPack. The combination of small diameter flimsy coax, the BNC connectors and constant moving of the unit while holding it caused 2 of my cables to fail at the connector. Be sure to bring spare cables or the means to repair them. Better yet, consider using a BNC to PL-259 adaptor so that you can use a heavier cable. The BNC mountings on the QPack are solid and I don’t think they will have a problem with the added strain. If you do manage to damage a BNC jack on the QPack it would be very easy to replace. I’ve also learned to do a better job when building BNC connectors. I’m sure I’ll have a better handle on this issue after Field Day and a few portable sessions.

6 Measurements

I spent my first day just experimenting with the QPack. I tried it with my home antennas as well as my homebrew portable verticals and a short NVIS dipole. After casual use I set out to measure it’s performance in a more organized fashion. The following charts show the QPack ability to tune a variety of antennas.

6.1 G5RV Dipole at 30 feet in trees.

My G5RV is a backup antenna. I use it when I have both HF rigs operating or when I want an antenna for east/west contacts on 20 meters. Here are the results of my tuning experiments.

Qpack Test						Equipment Used:
*Antenna: G5RV Dipole up 30' in trees.*						MFJ 269, Qpack tuner, IC-756 (for frequency & signal strength measurements)
*13-Jun-04*
Chris Levin, KB7YOU


Test Frequency		Qpack settings					Best SWR	Antenna Measurements without Qpack
Band	Freq (MHz)	Load	Out	Band	Tune	Gnd		R	X	SWR
160	1.80	--	--	--	--	Off	NO TUNE	9	27	5.7
	1.90	--	--	--	--	Off	NO TUNE	10	37	6.0
	2.00	--	--	--	--	Off	NO TUNE	11	48	6.5

80	3.50	3.4 T	3	3.5	1.9 T	Off	1.0	19	101	11.2
	3.75	3.2 T	4	3.5	2.0 B	Off	1.9	13	58	8.1
	4.00	9.7 T	4	3.5	1.1 B	Off	1.3	13	29	4.9

40	7.00	3.2 B	2	7	2.1 B	Off	1.0	25	28	2.6
	7.15