RFPM1 RF Meter Kit by vk3aqz Kits.


The RFPM1 RF Power Meter Kit by http://www.vk3aqzkits.com/   Let me preface this by saying, if this works 1/2 as good as the attention to detail that has gone into presenting this kit, it should  be nothing short of awesome. Opening the box is a WOW moment, as the level of detail and care that has gone into making this kit is evident. Lou VK3AQZ takes customer service to a whole new level, where most kits manufacturers give you a box and a bazillion parts, as well as a few photocopied pages, the RFPM1 RF Power Meter Kit is immaculately presented.


Key to the whole device is the RF probe, small parts contained in pill boxes to keep the separate and so they don’t get lost in transit is a really nice touch. You will also notice solder in 2 different gauges, one for SMT work and one for thought holes. That is just unheard of from anyone.


The case is well routed and drilled, so there are no expectations for you to cut and drill anything.


Parts for the rest of the unit are all contained within the case, both the analog and digital meters have been checked before leaving.

solar-rfmeter-10 solar-rfmeter-8

Build notes for both parts of the kit are in full colour, printed on laser, the kit contains 2 dvd’s showing the build process as well as many videos on how to use the unit for a number of different test scenarios. All parts have been ticked off the part list as they are packed and hand written notes about other bits not contained in that list have also been added.


The level of care and detail are very evident and Lou has really gone out of his way to produce a wonderful kit, made with high quality parts and I am looking forward to spending some time putting this together and using it in all the filter experiments i have planned. I might not have the money to buy an expensive frequency analyser, but with this and the 12mhz function generator I have, i can still find 3db points and measure the level of harmonics after low pass filtering. And one thing im looking forward to, is being able to set the gain on buffers used on mixers without having to convert rms volts into dbm, as this RF meter gives to the power in dB’s. Awesome.


Solar Panels for Portable

One thing i have found on the 3 day camping trips is that my battery gets pretty much hammered. Sure its 100ah, but after you have taken 40 to 50ah out of it, its pretty much done all it can do for the high current demands of a FT-897. When you see the voltage on TX get into the 11 and 10v range, you know you are not far away from hurting your battery permanently.
Maximum cycles and ultimately life of a deep cycle battery, can only be had if you do not discharge much more than 50% of the total battery capacity. Sure a deep cycle can be deeply cycled, but doing it often will lead to sulphation of the plates and poor holding capacity. Being the tight arse that I am HIHI, I wish for my cheap Chinese import battery to last for as many cycles as possible and with that in mind, i bought a solar charge kit.

So the kit i bought is a MaxRay 80w folding solar kit off Ebay. Total cost $140 delivered. Which comes with a 10A charge controller, 9m lead with 50A Anderson plug, carry bag and Anderson plug with battery clips.



Build quality seems ok, one small issue is the wiring to the charge controller was not done correctly, this is something i will rectify before i use it. Other than that, it seems like a nice enough unit. I will put it in the sun tomorrow and measure its voltage and current delivery to see just how close to spec it really is. That will be the real rest for this. But, if it keeps both our deep cycles charged for camping, it will mean i can take other high power devices and not have to worry about hurting the batteries. A fridge will be next and I think the boss wants a fan in the camper as well. HIHI.



Filters Filters and More Filters

Filters, its a huge subject with many books and millions of words devoted to trying to better understand the subject. Filters are the only real non amplifier stage in most radio designs. the covers a number of different types, Low Pass, High Pass, Band Pass, Notch, and come in a number of configurations, Chebychev, Butterworth, Cohn, Sallen Key and can be implemented either, passively with inductors and capacitors or with crystal or ceramic resonators or actively with Op Amps or CMOS Switched Capacitance.

So filters are by no means a trivial topic of learning, but one that can keep an interested person busy for quite a long time. It is also one I intend to fully explore over the next few months to try and come to a better understanding. Of all the filter types, i have only ever really built low pass filters for harmonic suppression in PA amplifiers. However, over the next few weeks I shall start experimenting with other filter types, starting with passive filters for audio, CW and SSB audio band pass filters, as these will be used in a Direct Conversion tranceiver project i have been working on for sometime on and off.

The next major filter type i wish to tackle is the crystal ladder filter, using ceramic resonators for 455khz 2nd IF of my Icom 718 radio. An Icom filter coast close to 300 bucks, a collins filter about 200 bucks, so i thought i would give the whole idea of home brewing a filter a go. Even if this is a total failure, i will have learned a lot about filter design and the motional parameters of xtals and ceramic resonators. Parts are on order from China, and as soon as they arrive I will start on the project.


To determine the motional parameters of a xtal or ceramic resonator you use a test rig like the schematic above. You insert a sine wave around the freq of the device into the input, measure the amplitude of the freq on the output with an rf meter, varying the frequency till you find the frequency that gives the maximum signal amplitude on each of the 3 sections, no capacitance, 10 and 27pf. With those numbers you can then do some math to get the series and parallel resonances of the xtals to use in designing the filter in a program like “Dishal” by DJ6EV.

More on filters to come.