DIY599 PA500 IC-705 Testing JS8Call

Hello Operators.

Overnight testing with the Icom ic-705 and the DIY 599 PA500 amplifier. The results were quite astonishing.

For the past couple of weeks I’ve been running 10 watts with the IC-705 & Microsoft Surface, and the chameleon skyloop or chameleon 40/20FD Fan Dipole. Honestly 10 watts with JS8Call is definitely enough to get on every continent.  10 watts is definitely enough to have a slow qso, but both stations are going to have to do some heavy lifting in addition to having low noisefloors. Here are a few results from past days/weeks overnight results.


When we put the PA500 inline with the 705 and an antenna with reasonable performance, we can see immediately a huge difference.

What we see when increasing the power three times, is more density in our sent and received signal reports. This isn’t just the amplifier, this is a combination of things which may not be apparent to the novice operator.

Using a combination of narrow bandwidth data modes, “enough” power, good antenna and a low noisefloor, we can achieve reliable communications with relatively low power. This is not true for voice communications, where the wideband signal is terribly inefficient, compared to our narrow bandwidth counterparts.

Off-Grid Perspective

There’s another reason for running the Icom ic-705 with the PA500. Firstly, operators often ask the question “Why not just use the 7300 or ft-891?”. The answer is current consumption! When the radio is just receiving, we want it to require as little current consumption as possible. Naturally this is from the perspective of the off grid operator, or someone intending on prolonged Communications with a finite amount of battery storage.

With our qrp radio and amplifier, the basic current consumption of the station just sitting there receiving, is under 300 milliamps. A QRO station running 100 Watts will not be a sustainable option in an off-grid environment. The amount of battery storage and solar required to keep the station up and running grows as current consumption increases.

The bottom line here is we can’t just look at using “more power” as a solution. When we’re talking about reliable Communications, we need to look at more narrow bandwidth data as an alternative to voice communications. We need to be able to augment our qrp stations, without shooting ourselves in the foot with battery storage. This means when augmenting our qrp stations, it should not require a truck sized battery storage system to power it. It means we need to keep our stations current consumption low, so that we can operate longer, but maintain that small qrp footprint.

Anyway, the PA500 has been absolutely magnificent! It certainly has added a layer of complexity to the station, I hadn’t wanted. But the benefits of this amplifier and qrp radio methodology, far outweigh any downsides. If you haven’t watched the PA500 video already, please take a look. You don’t need to get this amplifier, I’m only asking that you consider the station strategy.

Julian oh8stn

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