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Reviews Categories | QRP Radios (5 watts or less) | Oak Hills Research 100A Help

Reviews Summary for Oak Hills Research 100A
Oak Hills Research 100A Reviews: 48 Average rating: 4.9/5 MSRP: $129.95
Description: The Oak Hills Research OHR 100A single band CW transceiver kit
Product is in production.
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VE7TTJ Rating: 5/5 Jun 18, 2013 06:24 Send this review to a friend
Fab Rig.  Time owned: more than 12 months
This was my very first rig, which I built about ten years ago. Its performance is truly remarkable, its control logic simple and highly effective. Get the ten-turn pot, it really helps.

Construction was well-documented, no surprises, I took my time and enjoyed the process. It needs an external counter for readout, but that in no way detracts from the fact that when it comes to making and maintaining QSOs this is a

K0OD Rating: 5/5 Jun 12, 2013 05:35 Send this review to a friend
Fun Little Radio Even in a Major DX Contest  Time owned: more than 12 months
I selected the 40 meter OHR-100A kit last year as a dad and lad project. Even though my son was completing his BSEE degree, he had little experience with RF devices or soldering. Electrical engineering students these days computer model or breadboard projects; they rarely actually build them. To a Heath era ham like me, that situation had to be remedied.

My ham focus has always been on CW DXing and contesting. I saw the tiny size of most backpack-type kits as a negative. The OHR-100A is more of a QRP ďkilowattĒ that easily puts out 5 Watts (or just milliwatts by means of back panel pot). Other Eham reviews have amply covered the kitís construction. We spent an uneventful 20 hours assembling the 300+ parts. After touching up some marginal solder connections, the transceiver came to life.

Recently I returned my radio for alignment and repair after it died during a transmission. I figured its receiver hadnít performed up to potential anyway. Audio output had always seemed low, and narrowing the bandwidth control reduced signals excessively. Fast repair isnít an OHR strength. Their repair tech had taken seriously ill, however CEO Marshall Emm communicated with me quickly.

When the radio returned, the improvement was startling. Speaker output was much louder and the bandwidth control functioned properly. Marshall replaced a transistor or two that caused the transmitter failure.

My OHR-100a now SEEMED red hot. But would it perform in a real testÖ the ARRL DX Contest? Nothing beats a major DX contest for challenging the mettle of a station. I knew from past experience that I could make 40 meter DX contacts with 5 watts even with a Midwest QTH and vertical antenna.

My biggest contest concern was zero beating stations that used ultra narrow bandwidth filters. To be heard by them, I had to call almost precisely on their frequency, a chore with the OHRís varactor main tuning that covered 7.000 to about 7.077 in ĺ of a knob rotation. The optional 10X tuning pot, which I just bought, would have helped immensely. I also discovered after the contest that an outboard sharp audio filter enabled me to zero beat stations precisely.

The ARRL contest weekend yielded 73 contacts from 45 countries including several goodies: 3V8BB, 6V7S and 3D2RX. I avoided crowded prime evening hours and frequencies below 7.025 where the big boys ruled. My nice Tunisian Q, for example, was at 7.070 MHz around 0700Z. Two 6V alkaline batteries powered the radio all weekend.

Oak Hills optimistically specs the receiverís minimum bandwidth at 400 Hz, but thatís probably only at 3 dB down. A review in the December 2000 QST measured the bandwidth at 963 Hz. The 4-pole crystal filterís skirts are very broad. Strong stations even 2 KHz away were troublesome. Again, an outboard CW filter makes a world of difference.

Sensitivity is no problem. A/B testing showed that my OHR can hear anything detectable on my $2800 Flex-5000. Plan for drift of about 700 Hz for 10 minutes after a cold start, but almost none after 30 minutes. The basic OHR dial can be calibrated within 2 kHz. QSK worked perfectly even at contest speeds. A definite plus is the detent-centered RIT that tunes like silk across a +/- 1 KHz range.

Building the OHR-100a was a hoot for my son and me. The venerable design lacks the digital readout and precise tuning of a modern factory assembled QRP radio. I strongly recommend an outboard audio filter and multiturn tuning pot for serious QRP ops. While few will use the OHR-100A for a weekend of hard core DX contesting as I did, itís a capable basic transceiver and a pleasant construction project that deserves a 5/5 rating.
W9DDK Rating: 5/5 May 3, 2013 06:00 Send this review to a friend
Great experience Building 40m version  Time owned: 0 to 3 months
I have built ten-tec rigs but this one was great to work on. Completed and sent back to Marshall for alignment. He found several of my botched cold solder joints which he touched up for no cost. Marshall provided great feedback on my build to help me on my next one. Can t ask for better service or response when I had questions.

Receive is great and works great. Defintely will get follow up kits to go with this one.

Cant go wrong with Marshall and his business.
NZ0T Rating: 5/5 Jan 6, 2013 15:20 Send this review to a friend
Excellent kit.  Time owned: 0 to 3 months
Got the 40 meter version for Christmas this year. The build was enjoyable though it would have been better if there was a diagram for each step showing what area of the board the components were located at. I spent a lot of time searching for the correct place to place each component. Most kits I have built have that feature in the instruction book. There was a missing inductor but Marshall mailed one to me quickly even though OHR was closed for the holidays. The alignment went well using just my MFJ 259B's frequency counter, my K3 and a digital meter. The rig works very well puts out over 7 watts though I turned it down to 5 watts. I like the variable filter and it's nice to have RF gain also. It does drift for a few minutes when first turned on but stabilizes nicely after a few minutes. I have built a couple of the Ten Tec QRP kits which are nice rigs but the OHR 100A is a step up in my opinion.
K3KO Rating: 4/5 Feb 27, 2012 06:57 Send this review to a friend
Good surprise  Time owned: 0 to 3 months
Unit (with 10 turn pot) built with a few glitches along the way. One inductor was 100uh instead of 10uh. One FET installed in wrong place. After getting these solved, the unit played. Alignment by spreading/compressing turns of one inductor was a bit tricky. I set it a 2 Khz high in anticipation of the nail polish addition to hold turns in place. It still ended up 2KHz high. Broke TX offset adjustment cap. Fragile beastie. It didn't have enough range and an additional 22 pf had to be added to a replacement.

fter all these things were worked out my first QSO was with a UA0. You never know where you are frequency wise with a 10 turn pot. I added a digital panel meter voltmeter display hooked to the frequency determining pot wiper and mounted externally. It's not perfect but tells one freq withing 3 or 4 KHz for a cost of about $9. Good enough.

The drift from cold is the same as noted by another poster- 400Hz in the first 30 minutes. The next hour saw another 200 Hz drift-- about 3 Hz/min. Output is >5 watts. This is acceptable to me.
Overall I'm quite satisfied with the unit.

The 15 KHz pileup on 6O3A was way beyond what the RX could handle. Had to back off the RF gain to half!
KC2SIZ Rating: 5/5 Apr 27, 2011 05:48 Send this review to a friend
Fun to build and a solid performer  Time owned: 3 to 6 months
I built the OHR 100a and have had it on the air for a few months now. Its maximum output power is approximately 7 watts. The quality of the board and components is very good and assembly is not complicated. The receiver is excellent. Itís a very easy and intuitive radio to use. I love the bandwidth knob on the front panel, which allows you to adjust the receive bandwidth from 1200 hz to around 400 hz. (I wish it were that easy on my main station rig!) The QSK on this little rig is also astounding, and is as clean and smooth as Iíve ever heard on any rig. So, this radio has a lot of strengths to recommend it, and itís a lot of fun to build. Thereís really only one weakness I have noticed with this rig: It does have a tendency to drift a bit during the first hour or so of operation and especially during the first 30 minutes. One afternoon I recorded a drift of around 600 hz in the first half hour of operation from a cold start. So, I normally let it warm up for a while before operating and the drift isnít an issue then. However, I have also noticed that sitting something (like a speaker or keyer) on top of this rig (or removing it) will also affect the VFO. One day I moved a speaker from the top of the rig to a nearby shelf and all of a sudden the station I was working couldnít hear me! But these are things you just have to watch out for with small, home-built rigs like this. On the whole I think the OHR 100a is great and I recommend it without qualification.
EA5BLP Rating: 5/5 Jun 24, 2010 13:47 Send this review to a friend
Nice electronic design  Time owned: 6 to 12 months
I have built many kits and home brew radios and the OHR 100 is, without any kind of doubt,one of the best in the market. The electronic design of the kit is not based on the tipical reverse architecture. It has a well separated circuits for rx and tx.It admits also to connect a digital dial without any kind of problem. My experience with my 15m model has been very good. You can see the little toy in action here:

72 dx!
K4YAB Rating: 5/5 Jun 8, 2010 07:20 Send this review to a friend
Excellant Qrp Rig Priced Right  Time owned: 0 to 3 months
I just completed My OHR 100a.I had to use my Wife's Jewelry glass to Id the Caps and resistors. Most resistors were marked well.
I had the most trouble IDing the Disk Caps.
I had to go thru the alignment several times to get it correct.
When I finished alignment the rig was right on Freq and stable after a couple of mins or so.
The Rig has a excellant Ckt board and component
markings on it.
The Control Pots are the real deal and not cheap like the Control Pots in Ten Ten'S Qrp series KITS.
AA4K Rating: 5/5 May 24, 2010 10:40 Send this review to a friend
Excellent  Time owned: 0 to 3 months
I have been building radios for almost 40 years from
scratch and kits, the OHR100A 20 meters is one of the best.
K1KUZ Rating: 5/5 Apr 25, 2010 17:58 Send this review to a friend
Excellent radios! But a little word on soldering  Time owned: more than 12 months
Oak Hills Research makes a great kit rig in the 100A's,and I own four of them. They are easy to build and align, but if it does'nt fire up either in recieve or transmit, check your solder connections on the TOP side of the board! This has happened to me twice. The holes are supposed to be solder through holes, but they all might not make connection to the topside ground plane. If you don't see solder coming up through the holes on the topside you should add solder to that connection ON THE TOP of the board. this way you will avoid bad ground connections and possible trouble. I just thought I'd pass this info on so you don't have to send it back for service when it's a 99% chance it's only a bad ground connection! Have fun building!
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