W5EHS

Easily Heard Signals

Doing As I Say

htx 100I have done some checking and this weekend I plan to have the basic converter ordered that will allow me to get to a 144 MHz 2nd IF conversion from 28 MHz first stage transceiver. I don't have an all mode 2M transceiver. (More about that.) What I presently own is a HTX-100 10 meter only transceiver shown here on top of my Omni VII. It is one option I could use. What I definately need to get is a converter up to a low level 2 meter IF.

10MHz Standard Required

I have studied some of the super stable oscillators with rubidium and GPS locks mentioned in the previous post. I may get there with a bench standard or home station. The local ops and my friend KB8VAO in Ohio don't go to that extreme for portable operation, or need to... Neither do I for now. I will probably build an IsoTemp 10 MHz TCXO and plan on a compensated (GPS?) version later.

A high stability 10 MHz standard is required to feed converters to get to the microwave bands. My plan is to use the single standard to also stabilize the first stage equipment.

Premium Front End

I now have obtained a FLEX-1500 SDR (Software Defined Radio) front end with the superior software display of all signals in a wide bandwidth. Inaudible signals can be seen in the displays. SDRs do this with ease but are only designed for HF  through 6 meters (1.8 - 54 Mhz.) I need to find a suitable laptop before I can use the SDR in rover operation. I have just ordered a Down East Microwave L144-28IAC coverter.

So far this has been all talk and no show. Blogging it here will motivate my taking action! Ha!

Looking ahead, my next step will be building a 10 MHz standard for portable operation. Many more options there. Ahhh… I love the design engineering part and getting the plan to come together, my way.

Stability

I've taken a high interest in building and operating a station in the microwave bands. So I have been doing a lot of reading research on what it takes to make that happen. One critical requirement is obtaining the desired amount of frequency stability in the microwave frequencies.

As it turns out there are two approaches meaning two totally separate practices. Neither being right or wrong. It all depends on the desired form of communications. They are labeled broadband and narrow band.

Broad band is the most tolerant of frequency variations such as drifting and fluctuations. Those conditions are never desired but can be lived with, with less critical and expensive equipment design. For casual line of sight ham operations, broad band equipment is widely used.

For critical operations such as contesting, DX, moon bounce, meteor scatter and all weak signal work, very stable and accurate frequency control is required. Also the operator needs to know exactly what frequency on which he/she is operating.

Microwave frequencies are generated by mixing and multiplying and sometimes dividing super accurate base frequencies thousands of times. So a mere 2 Hz frequency change at 10 MHz can be a change of 2 Kilohertz at 10 Gigahertz. A change of .002 percent at the base frequency of 10 MHz is 20 Kilohertz and at 10 Gigahertz becomes 20 thousand Kilohertz or 20 MHz. How do you find a weak signal in that much bandwidth?

Extremely stable and very clean frequency control is absolutely necessary in weak signal microwave operations. All spurious noise must be minimal.

So for me it looks like project number one is to build a very stable frequency standard. 10 MHz is the usual base standard. Short term accuracies in the range of 5x10-12 can be obtained with some methods. That's 0.000000000005 percent!

That's less than a hertz or so at 10 GHz.

As soon as I decide on an exact design, oven regulated crystal, double oven regulated crystal, GPS controlled crystal, rubidium oscillator, rubidium/GPS hybrid, et.al., then I can start gathering components. This may very well be my first project build in this web site.