Hi all,
This is a simple blog to document some ham radio kit building experiences I'm gaining. I have no commercial or private connection to Oak Hills Research. I am solely commenting as a customer of this product and sharing my personal opinion. I purchased my kit at full list price and have received no preferential terms.
First blog is the OHR RFL-100 dummy load, a 100W (continuous) 50Ohm non-transmitting load for amateur radio transmitters.
I was unclear on how such dummy loads actually work, since if you search for these things on the internet you often see images of black, finned sci-fi devices or painters tins filled with oils or others that appear as metal bricks. After this kit, the concept and simplicity of these important devices is clear.
This kit from Oak Hills Research is a make-it-yourself item and is extremely easy to build - I finished mine in 1 1/2hrs, including coffee breaks! The quality of the crisp PCB, the weighty resistors, the excellent fit and finish of the all-metal case (expoxy and crinkle paint finished) and hardware were a joy to hold and behold.
I was so impressed with the invested attention to detail from Marshall Emm's (N1FN) company, that I've ordered more OHR kits to build, learn from and enjoy. I'll be adding to this blog as a record of those experiences.
In the end, my dummy load from OHR measured a final impedance (as presented at the SO235 socket) 49.7Ohm - a deviation of just 0.6% from perfection and well within the tolerances of 50Ohm +/-2% stated in the kit's instructions.
Since most rigs have a 50Ohm output impedance, they operate as intended when ideally connected to a 50Ohm load (max power transfer theorem!). Hence, these dummy loads should appear as 50Ohm.
From my measurements with a RigExpert antenna analyser the SWR measured from the OHR RFL-100 was noted as :
This is a simple blog to document some ham radio kit building experiences I'm gaining. I have no commercial or private connection to Oak Hills Research. I am solely commenting as a customer of this product and sharing my personal opinion. I purchased my kit at full list price and have received no preferential terms.
First blog is the OHR RFL-100 dummy load, a 100W (continuous) 50Ohm non-transmitting load for amateur radio transmitters.
I was unclear on how such dummy loads actually work, since if you search for these things on the internet you often see images of black, finned sci-fi devices or painters tins filled with oils or others that appear as metal bricks. After this kit, the concept and simplicity of these important devices is clear.
This kit from Oak Hills Research is a make-it-yourself item and is extremely easy to build - I finished mine in 1 1/2hrs, including coffee breaks! The quality of the crisp PCB, the weighty resistors, the excellent fit and finish of the all-metal case (expoxy and crinkle paint finished) and hardware were a joy to hold and behold.
I was so impressed with the invested attention to detail from Marshall Emm's (N1FN) company, that I've ordered more OHR kits to build, learn from and enjoy. I'll be adding to this blog as a record of those experiences.
In the end, my dummy load from OHR measured a final impedance (as presented at the SO235 socket) 49.7Ohm - a deviation of just 0.6% from perfection and well within the tolerances of 50Ohm +/-2% stated in the kit's instructions.
Since most rigs have a 50Ohm output impedance, they operate as intended when ideally connected to a 50Ohm load (max power transfer theorem!). Hence, these dummy loads should appear as 50Ohm.
From my measurements with a RigExpert antenna analyser the SWR measured from the OHR RFL-100 was noted as :
- 80m, SWR = 1.00
- 40m, SWR = 1.00
- 20m, SWR = 1.00
- 15m, SWR = 1.01
- 10m, SWR = 1.02
- 2m, SWR = 1.38
These are fantastic SWR ratios, given the load is from a kit and priced at $40 or so. Great value and by far equal to any commercial units available.
I present the build in a series of photos below:
Above: the return path of the RF circuit uses the aluminum case. So a metal to metal contact is needed between the SO235 mounting bolts and the chassis. To remove the quality paint job within the holes, I rubbed the holes out with a undersized drill bit to good effect.
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