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Reviews Categories | QRP Accessories | Norcal BLT Help


Reviews Summary for Norcal BLT
Norcal BLT Reviews: 6 Average rating: 4.7/5 MSRP: $$25
Description: Balanced line tuner kit
Product is in production.
More info: http://www.fix.net/~jparker/norcal/blt/blt.htm
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KX0R Rating: 5/5 Aug 16, 2007 11:17 Send this review to a friend
Great starting point for QRP tuner projects  Time owned: more than 12 months
(Please see other reviews of the BLT in the Antenna Tuners category on this site)

Other reviewers here have covered the main points of the Norcal BLT/Hendricks BLT well. This review deals with performance specs and how you can improve your BLT. This tuner is such a good product that I’ve built five versions, each with combinations of inductance and capacitance selected for different frequency ranges. My tests show that these tuners have impressive performance. By using a high-Q toroid inductor and polyvaricon capacitors, the size of the tuner is greatly reduced compared to conventional designs, while the efficiency is generally high. These tuners employ inductive coupling to a balanced secondary winding, and a relatively balanced output is obtained.

The “stock” BLT has a limited tuning range, and will match many resistive and reactive loads from 7 Mhz through 20 Mhz, plus a bit lower or higher depending on your combination of R and X. If you operate in the 7-22 Mhz range, you may find your “stock” unit satisfactory. It’s easy to modify a BLT for operation on higher frequencies, like 14-30 Mhz; likewise, you can modify a unit to cover a lower range, like 1.8-7 Mhz. While you can expand these ranges additionally with a few switches and capacitors, it would be difficult to cover 1.8-30 Mhz with one modified unit without sacrificing performance.

Just by changing the turns on the big toroid and by adding a few switches to the stock unit, you can have a much wider tuning range with better impedance matching. If you like mods and think the BLT is an easy project, consider adding some switches and tricks to extend the range. Ordering a stock BLT kit or two is a good place to start – then you can play around with it, once you understand how it works and where its limits are. Some of my units have gone through several revisions. The latest version nicely covers 20-60 Mhz.

If you need more info on mods, contact me by email: KX0R at ARRL dot net .

The modified BLT’s can match from a few ohms to over 1000 ohms, over more than two octaves, with reasonable efficiency. Efficiency drops for loads below about 10 ohms and above 1000 ohms (resistive), and correcting large amounts of reactance often makes things worse. Nevertheless, efficiency of over 90% usually is obtained with resistive loads in the 25 to 500 ohm range, with reasonable choices for L and C.

A simple, worthwhile mod allows switch-selected unbalanced (coaxial) output from the BLT, and this works nicely; efficiency is preserved. This is detailed in the BLT manual.

Using an MFJ-259B SWR analyzer, I determined that the match indicated by the Dan Tayloe LED matching bridge in the BLT is very close to 50 ohms resistive, from 1.8 Mhz to beyond 30 Mhz. If you adjust your BLT so the LED goes out, your rig will see 50 ohms in the “Operate” mode; it also will see a safe SWR in the “Tune” mode. The BLT may well save your finals. The “Tune” mode results in a 6 db loss through the tuner, a feature that may be useful while receiving or transmitting. The LED matching circuit will indicate with 1 watt or less, and it will withstand 5 watts mismatched for a long time.

Unfortunately the BLT is designed only for QRP. The polyvaricon capacitors employ very thin plastic for their dielectric, and this limits the voltage they can withstand. With reasonable impedances, they have no problem at 5 watts – maybe even 10 watts – but more power is risky, especially with a high-Z load.

Even though the BLT design delivers a relatively balanced output, this tuner is not a balun, and the design may not prevent common mode currents from flowing in a feedline system that’s inherently unbalanced, even when it’s adjusted for a perfect match. Unfortunately this is true of most tuners with balanced output circuits. Nevertheless, this won’t be a problem with most balanced antennas like loops and dipoles.

If you use a BLT for your QRP work, and you employ a balanced antenna like a loop or symmetric dipole, your BLT will allow you to use a high-impedance, low-loss feedline like UHF twinlead or ladder line, perhaps resulting in lower system losses than you might get by using coax feed. This is particularly true if you run the antenna off resonance, with a high SWR on your line, as when operating on bands other than what the antenna was cut for.

The BLT is smaller and maybe lighter than the combination of an unbalanced tuner like the Elecraft T1, a balun, and cables. The BLT is rugged, will match a wider range of impedances, and has no battery to go dead. Unlike most autotuners, the BLT presents a near-50 ohm load to your rig while tuning, protecting your finals.

At $45 the BLT is one of the best values available to QRP operators who want a versatile tuner. My only warning is that working with them is somewhat addictive – you may not be able to get along with just one.

George Carey Fuller KX0R
 
LNXAUTHOR Rating: 5/5 Nov 17, 2003 21:30 Send this review to a friend
A 'must have' FT-817 or QRP accessory!  Time owned: 0 to 3 months
- my hat is off to doug hendricks, KI6DS... i ordered this kit and received it very quickly...

- this is a wonderful tuner... all parts were included, and after a bit of soldering, i ended up with a great little QRP tuner...

- all parts were included... you can download a .pdf for the front and back panels that you can cut out and paste on the case to make the BLT look like a commercial product... hint: i printed out the .pdf panels, cut 'em out, then laminated each of the front and back panels, then glued each panel onto the case... the result is very professional and looks great!

- i have an FT-817, and use an LDG Z11 tuner with the rig... tuning with the Z11 (now discontinued) is fast and convenient... but i have found that the BLT can easily replace the Z11 for a number of reasons...

1. the Norcal BLT is a lot more convenient

2. the BLT is smaller and lighter

3. the BLT does not require any external power

4. the BLT has a built-in 4:1 balun

5. the BLT accepts balanced feedline, but with a simple mod, can take coax or random wire

6. tuning with the BLT can be just as fast, if not faster than the Z11...

- i modified my BLT... bolted on a wire from ground to ground out one of the balanced line inputs when desired... voila! a random wire tuner with no drilling of extra holes in the case... attach a counterpoise for better efficiency...

- if you have an FT-817 or other QRP rig, get this tuner... you will NOT be sorry! not only is the BLT a bargain ($41 CONUS), but you'll have a more flexible and easier to use tuner...

- the BLT is a great accessory for your kit bag... the tuner can handle 10W output... an additional benefit is the absorptive bridge provided by the tuner... you won't stress your rig's finals while tuning...

- the manual/construction guide is available via the amqrp.org Web site...

- once in while you run across a good deal in ham radio equipment - the Norcal BLT is one of these deals!
 
KC8AON Rating: 5/5 Sep 1, 2003 07:34 Send this review to a friend
Super QRP Tuner !  Time owned: 0 to 3 months
I bought one of the new kits with the new aluminum enclosure, and I must say, "It's very easy to build, and a very rugged little tuner". It would make a very compact tuner for field operation for 10 thru 40 meter operation. The LED swr indicator is very visible even in sunlight, although I would suggest to shade it when fine tuning to get the led to go out. So far, it has had no trouble tuning my 40 meter extended double zepp that is fed with 450 ohm window line. Having only 2 controls (variable capacitors), tuning is very quick ! I added the unbalanced mods to mine when I built it, and this makes it a good single end fed wire tuner - very handy for field operation. Just throw a wire up in a tree, tune it up & you're on the air ! I would recommend it to anyone needing a compact, rugged QRP tuner.

72/73
Rick McKee, KC8AON
FPqrp #33
 
N0TYC Rating: 5/5 Jul 17, 2003 03:46 Send this review to a friend
updated BLT case/price  Time owned: 0 to 3 months
Got to play with one a bit, and was impressed. I just put my check in the mail. I'll follow up after I've built my own.

Note that the case has just recently been changed to a custom aluminum clamshell (no more PC-board+plastic cover), with the end covers pre-drilled. The new kits are also going to come with a "Pittsburg Style" etched PC board, so it is no longer really Manhattan-style. They also increased the price by $10.

Finally there is a better URL for current information on the kit: http://www.amqrp.org/kits/blt/index.html
 
WA1GJF Rating: 4/5 Dec 28, 2002 19:52 Send this review to a friend
It Does Work!  Time owned: 3 to 6 months
Assembly was fairly straightforward, but the assembly area was somewhat cramped. The switches supplied did not survive much heat from soldering, so be careful! Once put together, it is amazing how well it works. I have an inside antenna that the BLT tunes well from 30-10 meters. 40 is a stretch, but it could be the "walt disney" (read mickey mouse) installation of the antenna in the attic. Winding the toroids was a snap but mounting the parts took patience, and some Dr. Daniels. Yes, I would buy another & recommend it.
 
KD5KXF Rating: 4/5 Aug 17, 2001 11:40 Send this review to a friend
Great QRP antenna tuner  Time owned: 0 to 3 months
This tuner is designed for balanced line fed antenna's but can me easily modified to work on unbalanced feedlines as well and works for QRP power levels 40 meters thru 10. It has the LED swr meter which makes it very useful for these lower powered kits like SMK1 and Tunatins. Try tuning those on a QRO tuner and you will understand what I mean! The kit includes EVERYTHING. Every switch screw nut wire and even the case. It is built manhattan style and has clear instructions. The case is built from pcboard. The only thing I didn't like was the plastic case cover but after I built a PCB material cover that was no longer a problem. (that is why I gave it a 4) I use it portable with a SST and it has survived all my trips and tuned zipwire dipoles, inverted v's fed with tv twinlead and my BW20 vertical. Great deal on a REALLY useful little tuner. This would make a fine 2nd kit! Operation with it is a 5!
 


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