How do you get yours up? Antenna that is...
Total Voters: 37
Here’s an email from my good friend and cohort in the Central Florida QRP Group. Jim wanted to share his latest mods for the Rockmites and some thoughts on the NEScaf filter. I think you will enjoy his notes too …
Kelly,
I thought I would bring you up to date on my latest project. I just finished a Small Wonder 20+ and used it on the Flight of the Bumblebees. I found my earbuds a little weak on audio output and the IF bandwidth of the SW20+ a bit wide for my liking. I read the specifications on the NEScaf filter offered by the New England QRP group and decided that that would be the best solution to my problem and be usable on other radios as well. I ordered, built and installed the NEScaf board in a TenTec TG-24 enclosure. I tried it on the SW20 and it sounded like a viable solution.
The Rockmite and NEScaf filter in Ten Tec Enclosures
I also have a 40 Meter Rockmite in a TG-24 enclosure and decided I would see how well the RM/NEScaf combination sounded. The Rockmite, of course, uses a DC receiver and the bandwidth is determined by the upper response of your ears… My RM sounds like about 40 khz wide, hears the whole band for me as my response is in the upper tens of kHz. Yes, I know, at my age 69 it shouldn’t be but is. Been tested. At any rate suddenly the Rockmite bandwidth is manageable. I had some audio artifacts, whistles and the RM sidetone would drive the NEScaf into cutoff which only a power cycle would clear. I googled the problem and Charlie KE2SP advised lowering the NEScaf input Z with a 10 to 47 ohm input load. I installed a 27 ohm resistor on the input connector and suddenly all artifacts, whistles and sidetone problems disappeared. WOW, the RM is really sounding great! Except the RX/TX was very low. I measured it at 500 cycles and the NEScaf would not tune down that low…
Closer Look at the Finished Rockmite and NEScaf
After considering several approaches to the problem and considering that the RM crystals don’t oscillate on exactly the QRP frequencies, I settled on completely revamping the RX/TX method used in the RM. Using the RM40 as a test bed, I removed D5, D6, R9 and R10. I purchased 2 Murata trimmers( TZ03 Series) from Skycraft, our local Surplus emporium, and installed them in the holes for D6 and D5, R9 combination of holes. I had to cut a small run on the right side (antenna connector side) to isolate that pad from Vcc and jumper to two trimmers together… I also had to drill out the pads to accept the trimmer leads. The Fet Q2 does a great job in switching to second trimmer in and out for the offset. The alignment was not difficult but I recommend using a freq counter connected thru a times 10 scope probe to the physical top of R5 (base of Q5). Don’t have to key the Tx to see the freq… I set the trimmer in the D6 position for the higher freq (7.030750 Mhz) and the other trimmer for the lower frequency (7.030000 Mhz. The trimmers I use are available at Digikey. I used the Red colored model (4.2 to 20pf, N750) but the Blue colored (2.7 to 10pf, NPO) might have been a better choice. These guys are Digikey p/n 490-1971-ND and are $0.43 each… I also changed the RM40 volume control from an audio control (1 Megohm) to a RF front end attenuator control (1.5 kohm) and there is a noticeable improvement in the overload and broadcaster breakthru problem. I strongly recommend these changes. If you can build the RM you can certainly modify it… If you break it, build another… I plan to make the same modification to my RM80. (CLICK THE THUMBNAILS for larger view)
Rockmite Mode Closeup 1
Rockmite another closeup
The Inner Workings of the NEScaf and Rockmite
How did it work? Well, the RM/Nescaf stack is now a real radio not just a toy. I worked WD8MHT Raul in Waynesville, NC one morning this week and we had a great conversation. He was 569 to me and I was 439 to him. His TS570 was working hard but copied me no problem. The amazing thing for me was that there was a really strong signal at 700 cycles and Raul was about 200 cycles higher. I tuned the Nescaf center freq on Raul and sharpened the bandpass and turned up the volume and he was armchair copy the entire QSO… WOW, not a struggle… I have since used the NEScaf on my SW20+ and yes, it works great…
I have attached a couple of pictures of the stack and the innards of the RM for reference. The switch on the front is for a future expansion.
72
Jim
K4AHO
Now into the third week of my sabbatical, I am surprised how much I want to get out and operate my QRP portable gear. Guess I have deprived myself over the years of being a confirmed workaholic and avoiding time off, vacations, and time for my favorite hobby.
Grrrrr! The Polar Bears Are On The Loose!
This should be a good weekend for QRP portable. The Polar Bear QRP Group will be out for another Polar Bear Summer Picnic Event and Polar Bears from Spain to the West Coast of the US will be out looking for BSO’s. Grrrrr! I am PB #173 and we’re over 200 members now. With the new Twitter and APRS connections to QRPSPOTS.COM which also point to the excellent spotting site of K3UK with a section for FISTS/QRP Ops to spot and sked one another, there are plenty of ways to use technology to help find each other. Add in a few other contests and state QSO parties, and there should be some buzzing going on this weekend. Makes me wonder when the FOBB results will be announced! Buzzzz Buzzzzz
I’ll be out and if all goes well I will be field testing a new C Pole antenna based on the suggestion I received from Neil W0LVZ. I added some switchable capacitance to my BLT+ and have rewound the main toroid to see if I can push the range a bit more with it so will have a delta loop and probably my W3EDP in the air too. I love playing with antennas and am still amazed when the ones I build actually make contacts!
Give a listen for me on the QRP watering holes on 40m, 30m and 20m Saturday morning. I’ll be self spotting on QRPSPOTS and the K3UK sites to make it easier for you to find me. Let me know how my newest antenna is workin’.
72,
Kelly K4UPG
PB #173
Had a good day in the park with Jim K4AHO and Wally KG4LAL. Spent a good bit of time testing a couple tuners for End Fed Half Wave antennas using Jim’s AIM 4170. Wow is that thing a great tool for tweaking antennas! Info overload!
I built an antenna tuner based on AA5TB’s design for an end fed half wave antenna. I am using a 3 ft or so counterpoise on the ground as Steve suggests. On the analyzer in a test lashup it was a bit touchy to hand capacitance but tuned well even up to 21Mhz. Since I am not thinking of backpack size I used a pretty good sized enclosure for it. I am using an air variable 6-160pf cap instead of a polyvaricon like Steve used since space is not a big issue. I also used a T68-6 toroid instead of the T50-2 Steve used.
When I mounted it in a plastic box the sensitivity seemed to increase. I have not put a LED SWR bridge in the box yet, as I was waiting to see how it worked before adding more variables. Today I was able to put an AIM 4170 analyzer on it and it did tune the antenna… seems that the air variable I used is perhaps a tad small. It is almost fully meshed on 40m cw and on 20m it acts like even at minimum capacitance the sweet spot is very narrow and hard to tune.
Here's the innards
My question(s) are: 1) Is the hand/body capacitance normal? If not, what might cause it to be so touchy? 2) Would my parts layout be part of the issue? 3) Does the DPDT switch (mini toggle) I added for later use with the SWR bridge add significant capacitance to the circuit? I was able to match a 21Mhz load on the raw test setup, but not once it is in the box. 4) I have a small bus wire for a ground, do I need to increase that? 5) Is the plastic box the problem? Would it be better in a metal enclosure? 6) Am I asking too many questions? Sorry, this is how I learn. Build, test, ask…
SWR bridge I want to use
Thanks for your wisdom and experience on this one.
72, Kelly K4UPG
As one of the many antenna restricted condo owners of America, I cannot operate as often as I’d like. The hassle of putting up and taking down temporary antennas wastes time, isn’t always practical and generally spoils the fun for us.
Great that we have some holidays and time off as it allows a bit more opportunity to get on the air. The MI QRP group hosted a 4th of July Sprint and although the hour was late (7-11PM EDT) since I did not have to go to work Monday, I took advantage of the chance to work a few of my fellow QRP ops.
Rain and lightning welcomed my efforts to set up an antenna. So I forsook my normal setup and settled for a twinlead 44 foot doublet hung from my 20 foot Jackite pole which was bungee cord strapped to a ladder in the back yard of our condo. The antenna ran north south so much less than ideal, but at least I could get on the air.
Freshly Built NEScaf saved my bacon!
The day was saved by my freshly built NEScaf filter. As one of the lucky ones, I recently received the latest edition of this great kit provided by the NE QRP bunch. It enabled me to listen to cw despite the high QRN and background hash from neighbor’s TV’s, computers and air conditioners. What a joy it is to actually hear stations through the noise. This is a must have accessory for the condo based QRP op! I am still learning to use it well, but am mega-impressed with the capabilities it offers. With this audio filter, I could null out the QRN and peak the CW signals making for much more relaxed and enjoyable copy. The extra audio boost helps my little Sierra audio too. Keep watching for the next round of kits!
45F a bit of sun and a lot of wind! Today I escaped being selected for jury duty so opted to get the oil changed in my car! I called and my shop was not too busy and said, “come on down!” So I packed my 30m SST, BLT+ tuner and accessories and took off. Instead of sitting in the waiting area and reading out of date magazines and watching silly game shows, I walked out to the parking lot and threw some wire into a couple small trees. I only got the main 46 feet wire up about 15 feet on one end and sloped it through another small tree and out to my camping table. I ran a counterpoise of 23 feet to the same small tree and hooked up my trusty BLT+ tuner.
My Oil Change Parking Lot QTH for 30m
A quick tune found a couple week signals. I tuned the antenna a bit, called CQ with no luck, then heard a decent 579 signal calling CQ. Bill, NG3O in Columbia, MD replied and although I wasn’t strong (539) he thought he could copy me. He sure did a great job and we enjoyed a nice QSO for almost 30 minutes. Sure is pleasant to work a good fist without any QRM. He said I was his first Oil Change Parking Lot QSO.
A few minutes later, I connected with Rudy, W8RJW in Columbia, SC. He was a strong 589 and gave me a 559. We had a nice qso for several minutes too. It was a fun way to pass the time while I waited on my car maintenance to be done.
The band got pretty quiet afterwards and though I heard a few more stations, it was time to pull the plug, take down the wire and go home. I think I have figured out a new way to pass time when the opportunity is present. Hope you will give it a try too!
Kelly demonstrates the strong arm method (aka sore arm)
Today a post by an unnamed fellow Polar Bear QRP op (and antenna tweaker) inspired me. His post about multiple sockets and yellow string hanging in the tree in his back yard generated a good bit of fun as others reminisced and told their own funny story about the perils of getting wire up into a tree.
So, in a followup to the favorite antenna poll of the last two weeks, I decided to open a poll to determine the QRP portable operator’s favorite method of getting your portable antenna up in the tree.
Most of us have a sore arm or other memory as we learned our own preferred method… so here’s your chance. Vote for your favorite and leave a comment and share your antenna launching story. Come on now… let it out!
Almost time for another Polar Bear Moonlight Madness Event! Grrrrrrrrr! This coming weekend, Saturday 14 Nov 2009, Polar Bears will be clamoring for position in the ice field and slammin pawerful signals into the air. Bring a rig and join us.
K4UPG Bear pounding brass and gittin' ready for the PBMME!
K4UPG Bear #173 is excited because some other bears is gonna be gathering with the Central Florida QRP Group which is scheduled to meet that same day! So come on out to the Cracker Barrel in Sanford, FL for some sammin pancakes or sumpin else at 0730 EDT breakfast time. If you cannot make the feeding, then meet up with the rest of us bears at Sylvan Lake Park in the A Pavillion area at around 0900 EDT. Ya’ll come, hear??? Grrrrrrrrr!
Grrrrrrr! Brand new Polar Bear #173 ventured out to Lake Fredrica today to stir up some fellow PB’s on the air. Setting up the mini bac Delta Loop Beartenna went well and I started on 40m. The band was OK, but I couldn’t seem to raise any BSO’s with my fellow Polar Bears. After a few minutes I switched to 20m with my Wilderness Sierra and WOW! The band was full of California ops in some sort of contest. Most of them blew me away with their fast CW and very strong signals but it was good to hear so much cw activity and the band was pretty good.
I setup my trusty Buddistick for 30m and almost got a perfect SWR. My Wilderness SST on 30m was hearing a good bit of activity and I managed brief qso’s with fellow Polar Bear QRP members W05X and N9SKN despite pretty heavy QSB on both signals. I heard W6BBQ and WG0AT but could not get a reply when I called them.
A bit later the band opened to Europe and I also was hearing West Coast (California and Washington) stations. I came back to S57MU and he gave me a 559 into Slovenia! Not bad for 2.1 watts out and it was a good way to end a fun day.
Thanks to the Polar Bear QRP Group for allowing this baby bear to participate. I look forward to future portable events and I’ll keep workin’ on a super-duper Beartenna so I can hear ya’ll even better. Grrrrr!
PBMME Oct 09 portable site at Lake Fredrica Orlando, FL
Tuning for Bears on 30m
My project this week was a Ten Tec 1051 Noise Bridge. I used a Ten Tec enclosure and it all went together quickly and even worked on the first try! It is a sweet tool for tuning an antenna when using a tuner without putting a signal on the air. I think it will help me and my BLT+ find the sweet spot a good bit faster than doing it otherwise. In the future, I plan to upgrade it to a full RX bridge so I can do some measurements too. Here it is…
TT 1051 rear view
TT 1051 Noise Bridge simple front view
I took my radio with me to St Louis and tried my hand at Hotel Portable ops. The conference schedule did not allow me much time, but I did get a break one afternoon and took 30 min to play radio in the courtyard. I threw my Coleman Clothesline reel over a tree limb at about 15 feet and paid out about 30 feet of wire and placed about 16 feet of wire on the ground as a counterpoise. It loaded well on 40m with my BLT+ and I worked three stations in about 20 min. Not bad!
St Louis Hotel Portable Airport Hilton
St Louis Airport Hilton Loading the Window frame!
After returning home, the weather in Orlando was great and I hit the nearby lake park for some antenna testing with a Mini Bac in various configurations. I was really happy with the Delta Loop which loaded well on 20m and 40m. This antenna is a keeper and I’ll be doing more testing and learning about how to deploy it.
Lake Fredrica operating position
Buddistick deployed for comparison
Here is the Delta Loop! Can you see the 26 gauge teflon coated wire? Here is a link to an outlined view of the Delta loop. CLICK HERE. The Red line is the feed line which is twisted 1 turn per foot and held together with masking tape. Pretty slick. The “insulator” I used is also masking tape, as are the corner point markers and peak of the Delta. As I measured it I stuck a small piece of tape on the wire.
Mini Bac antenna in 14MHz Delta Loop Configuration
At last! We finally had a break in the weather and did not have thunderstorms and rain all weekend! Although it was hot, it was really nice to be out byLake Fredrica and set up antennas again. My trusty slingshot worked well and I managed to get a line over a couple limbs on the tall pine trees for a 40m dipole up at 40 feet. The dipole was fed with 300 ohm twinlead and loaded up well with my BLT+
Can you see that dipole in between the pine trees?
Kept moving to stay in the shade!
20 ft Jackite pole and 44 ft doublet first test setup
Dr Pepper and CW QSO's what a treat!
My wife saved the day by bringing me a cold Diet Dr. Pepper after I’d been baking in the Florida sun for about 4 hours. What a treat that was, eh?
Band was not too great with a lot of QRN and some SSB and RTTY QRM later in the day. My 20 ft Jackite pole and 44 doublet as an inverted vee with the ends 3 ft off the ground was disappointing test. My BLT+ would not tune it on any band I tried.
I posted that result to QRP-L reflector and the MQFD list and got a good number of replies. Seems that anything less than 6 feet above ground makes the 44 ft doublet difficult to tune! So I’ll be trying different configuration the next time out and see how it goes.
Maybe I’ll have my new halfwave end fed tuner completed soon and have some time to test it out and report those results soon too. I love this QRP stuff!
My hat made a good sunshade for the Sierra
