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Reviews Categories | Antenna Tuners | Hendrick's BLT Antenna Tuner Help


Reviews Summary for Hendrick's BLT Antenna Tuner
Hendrick's BLT Antenna Tuner Reviews: 8 Average rating: 4.9/5 MSRP: $46
Description: The BLT is a simple Z-Match tuner that works from 10-40 meters
Product is in production.
More info: http://www.qrpkits.com/norcal_blt.htm
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You can write your own review of the Hendrick's BLT Antenna Tuner.

XE2XX Rating: 5/5 Jan 22, 2012 19:18 Send this review to a friend
Works fine with my Yaesu FT817  Time owned: more than 12 months
Winding toroids is not much fun for me but the 2 ones in this kit are not complicated. Actually it was harder placing the decals. The tuner is easy to operate. I have no problem to make the calibration when the antenna is in the swr range the unit can handle.
 
KJ6MSG Rating: 5/5 Nov 6, 2011 17:49 Send this review to a friend
Amazing little device.  Time owned: 3 to 6 months
Using an FT-450D and a simple speaker wire dipole, I made multiple DX contacts from my location in California (T32C and Russia, most noticeably) on just 5W SSB using the BLT+. It's easy to build (though counting the toroid windings is naturally a pain in the butt) and easy to use. It worked easily on 40-10m with no issues. I would easily buy another one.
 
N6EY Rating: 4/5 Sep 12, 2010 20:52 Send this review to a friend
Great kit - a must have QRP tuner!  Time owned: 0 to 3 months
This is a well designed, well documented kit. The Tayloe SWR indicator kit is an excellent addition to the tuner.

Two things I would offer for improvement: First, while the documentation is well written and detailed, the SWR indicator documentation and the tuner documentation don't exactly match, so they require some correlation. Beginners may find that challenging.

Second, the supplied binding posts are inexpensive - great fillers for the kit, but I found they are fragile and the threads strip easily.

Overall, very much worth the money and the time to assemble. It's a great tuner and you'll be up and running in no time! Buy it today!
 
KB3ONA Rating: 5/5 Oct 19, 2008 13:08 Send this review to a friend
Great Tuner  Time owned: 0 to 3 months
I ordered the BLT online and received it in the mail within a few days. This was my second kit so I appreciated the well-written instructions with photo's. I assembled the kit in about 5 hours over 3 evenings. Everything went together without a hitch. I gave her a trial run in my shack on 20m, 30m, and 40m on both a vertical wire antenna cut for 30m and a full wave 40m loop. The tuner easily matched both antenna's on those bands so I was quite happy. I haven't tried it on the higher bands but I read you should reduce the number of windings in the primary coil to match loads above 20m. I'll give that a try on the next BLT I order. All in all it's a great value.
 
KX0R Rating: 5/5 Aug 16, 2007 11:13 Send this review to a friend
Great starting point for QRP tuner projects  Time owned: more than 12 months
Other reviewers here have covered the main points of the 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
 
NE4U Rating: 5/5 May 16, 2007 08:59 Send this review to a friend
fun and functional kit  Time owned: 0 to 3 months
I'm fairly new to melting solder and kit building, so I faced this project with a bit of trepidation. The kit comes with a small PCB that requires you to melt solder on the pads before adding resistors, capacitors, leads to the toroids, etc. Then, there was the winding of the toroids to face. And lastly, dealing with the small size of the enclosure...

BUT...this is not a hard kit to build! Doug was very responsive to questions throughout the build and, although he checks things before they go out the door, sent a screw that was missing from my particular kit in short order.

There are a lot of little wires inside a tiny space. Sometimes I had a bit of difficulty keeping the resistors on the tinned pads from falling down when I applied heat to them to add hook-up wire and components near the end of the build. The toroids were easily wound, leads tinned, and connected. I'm quite happy how it turned out!

I hope to add the modifications to the kit that allow it to tune wires other than balanced lines. The aluminum case was easily drilled through using my Dremel and a cordless power drill.

The best thing is that once I hooked this device to my Rock-Mite 40m it tuned up my Crappie Antenna just fine!

Here are some photos of the build if you're interested. Thanks, Doug!

http://flickr.com/photos/shadle/sets/72157600123807510/

-john W4PAH
 
KB5JO Rating: 5/5 Feb 8, 2007 13:20 Send this review to a friend
Great Little Tuner  Time owned: 6 to 12 months
I'll echo W0PQ's review, with the exception that mine will effectively tune 40,30,& 20 but not 15 when feeding my 88 ft doublet. Of course this has more to do with the length of my 300 ohm feedline than any deficiencies on the BLT's part.

I built this little tuner for my QRP rigs and was thinking of using it for park bench portable operation. Actually, I use it every day here at home. It was easily assembled, the price was right, it works as advertised.

I incorporated the modifications suggested in the plans adding BNC connector and switch to permit feeding coax, but haven't used it yet.
 
W0PQ Rating: 5/5 Dec 10, 2006 20:37 Send this review to a friend
Great Little QRP Tuner  Time owned: 0 to 3 months
"It's better to be silent and thought a fool than speak and remove all doubt". Abraham Lincoln

The above quote came to mind as I prepared this review. My purpose for writing this is to elicit comment and comparisons from others who have assembled the Hendrick's BLT QRP antenna tuner kit.

The price was fair, shipment was prompt and the kit has everything including a sturdy 4 piece case.

Holes for mounting the controls and terminals are predrilled except for holes for fastening the tuning bridge printed circuit board and the grounding lug for the antenna toroid center tap. I drilled a hole in the bottom of the case to fasten the printed circuit board and then used a counter sink drill so that a bevel head screw is flush with the bottom of the case. For the toroid center tap ground, I did not drill a hole. Instead, I fabricated a solder lug that fit behind one of the balanced antenna tuner terminals and soldered the toroid center tap to it. I secured the toroid and an insulating pad made from milk carton plastic to the bottom of the case with super glue.

The pc board is small and the components and connections are in a dense pattern. Be careful not to make solder bridges from the "Pittsburgh" type pads to the foil surface surrounding the pads or to adjacent pads. A printed circuit board vice is a great help.

The method of preparing and soldering the resistors that the instructions call for requires a third hand to hold the vertical resistors in place while applying solder in tight places.

Solder the two connections going to the front panel switch at the top of the resistors, not at the pad end. Observe polarity when mounting the 1N34A diode. The short lead of the LED goes to ground.

Check the following resistances to ground while the operate/tune switch is in the operate position. The junction of R1 to R2 = 75 ohms. The junction of R2 to R3 = 50 ohms. Polarity doesn't matter.

The large toroid windings are difficult to count if they are the same color wire. I recommend using the red magnet wire for the primary as the instructions call for. Use different colored plastic covered hook-up wire for the two secondary windings. I also think it's better to leave the ends long and use them to hook up directly to the antenna tuning capacitor and the Lo Z/Hi Z switch.

The toggle switches are easily destroyed by a hot soldering iron. Tin the leads and touch the soldering iron briefly on the switch terminals.

My QRP rig is an Elecraft K1-4 running 5 watts and equipped with an automatic antenna tuner. My antenna is a 102 ft. G5RV up 40 ft. and fed with 300 ohm hi-grade twin lead. The BLT QRP tuner's primary purpose in my case is to provide a balanced output to the G5RV, but it also serves as an antenna matching device in tandem with my K1 automatic antenna tuner.

Hendrick's web site and others say the tuner is capable of 40M through 10M operation. The tuner meets my expectations on 40, 30 and 15M but NOT on 20M. I've made several contacts on 40, 30 and 20M. On 40, 30 and 15M I can hear a definite peak in noise when I rotate the antenna capacitor. When I throw the SWR switch I can easily tweek both variable tuning capacitors to extinguish the LED on 40, 30 and 15M but not on 20M.

Both Lo Z and Hi Z balanced output settings work for 40, 30 and 15M. Lo Z works better for 20M. These results are with both transmitter and antenna tuning polycaps, C2 & C3, untouched from the factory setting. In other words, no change in the trimmer capacitors.

For 20M I set the the antenna capacitor at the maximum clockwise position (minimum capacity). Rocking the transmitter capacitor through the 1 o'clock position noticeably dims the LED but doesn't completely extinguish it as on the other bands. I've made enough 20M contacts to feel confident that this tuner works as well as the my MFJ-949E tuner, even though I can not achieve a complete LED null on that band. The K1 automatic antenna tuner always finds a perfect match on 20M when I set the antenna tuner capacitors as described above.

A note in the circuit diagram says "C2, C3 are 140/80 polycaps with sections in parallel. Be sure to set trimmers to 0." The instructions call for the main sections to be wired in parallel making them 10 - 220pf. I've experimented by changing the trimmer capacitors to their minimum and maximum settings with no significant changes in the operation of the tuner.

When assembling the tuning capacitors I oriented the tuning knobs so the knob pointer is at 12 o'clock when the tuning capacitors are at mid-range of their 180 degree sweep. One improvement I've made was to disconnect the 80pf section of the 2-section antenna capacitor. The results on 40M-15M are identical to those when the 80 pf section is connected but the LED nulls are broader and easier to tune. 40M and 30M nulls also fall nearer the mid range of the tuning capacitor.

There are circumstances when one may wish to use a random length of wire for an end-fed antenna. Not having one, I merely used one side of my 300 ohm feed line to the G5RV, disconnected the other side of the feed line from the tuner and then grounded that antenna tuner terminal to the chassis of the QRP tuner. I chose 40M and 20M as test bands. The QRP tuner demonstrates a match on both bands as indicated by a complete null of the QRP tuner LED. I heard strong signals on both bands but on 20M I noticed a high level of noise when using this unbalanced arrangement.

Dipole antenna theory holds that an impedance mismatch between the feed line and the antenna center feed point results in a standing wave along the feed line no matter what the tuner settings are or what the the SWR indicator displays. In most cases, if low-loss twin lead, ladder line or open feed line (300-450-600 ohm) is used the standing wave will not detract significantly from radiated power.

Maybe I'm making too much of not being able to achieve a complete LED null on 20M as I do on 40, 30 and 15M. My G5RV antenna seems to present a reactive impedance on 20M that is a little beyond the range of this tuner. I intend to experiment by chopping off some length of my twin lead to find a length (an area of a standing wave) that presents a better impedance on 20M. I'm curious what others have noticed about this remarkable little tuner with regard to its performance using various types of antennas and feed lines.

 


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