The Virtual COM Port

All current production RF Concepts products have some means whereby a computer can communicate with them. With the advent of USB, we have had to change the interface to keep pace with where computers are going.

Many of us can remember the 25-pin RS232 standard interface. This standard was introduced in 1962, and was usually used as the way electromechanical teletype devices were connected to a modem. As personal computers became common, it became the standard for numerous interfaces, such as from the PC to a terminal or a modem etc. My first computer was an S-100 bus type, and used two 25-pin RS232 interfaces, one of which went to a VT52 terminal, and the other to a Hayes 300 baud modem. Hot stuff, at that time! The IBM PS2 family adopted a 9-pin version of the standard, which provided virtually identical functionality, but in a more compact physical form. With more "smarts", it was possible to manage the communications flow over the interface with fewer "supervisory" signals, such as DTR etc., and hence go from 25 pins down to 9.  When the need for an even higher performance standard was addressed, it was realized that there was no need for any such supervisory and control signals - all of the management of the interface could be achieved through serial data transfer commands. This is how USB works - there really are only four wires in the USB interface- two wires for bidirectional data transmit/receive, ground and +5V. This allows for a very small connector, and with care, very high data transfer rates. As PC's gave birth to laptops, and then notebooks, and now minis, the space available on the side of the equipment for interfaces got smaller and smaller. I remember suddenly realizing that it was almost impossible to buy a notebook PC with a 9-pin PS2 interface any more.

For all versions of the standard, when you plug it in to a IBM PC compatible computer, the interface showed up as a COM (communications) port, mapped to the PC's "IO space". On older equipment, you could change jumpers on your serial card to make a serial port go from "COM1" to "COM2". In those days having more than four COM ports was rare, but as time went by the need for more COM ports went up- modems, scanners, printers, mouse... In principal, the I/O mapping could allow for up to 256 COM ports, although there are reasons why this was never achieved. One of my last projects in the RS232 world had a server with provision for 32 modems to be plugged in, mapped to COM1 through COM32......

The Alpha product line has followed this along in the same way. The 87A has a 25-pin RS232 connector on it. The 4500 family of wattmeters has a 9-pin PS2 type connector. The 9500 has both a 9-pin RS232 and a USB port; and the 8410 has only a USB port. Future products are likely to continue to have a USB port on them.

If you want to interface your PC to one of the Alpha products that has a traditional RS232 port, and your PC only has USB, the first thing is to get a USB-to-RS232 adapter. There are several manufacturers of these, and we can supply one that has the ability to adapt to both 9-pin and 25-pin interfaces, so it can be used with an 87A or a 4510, for example. In fact, inside the 9500 and 4510, there really is a "hidden" USB-serial converter. The following discussion applies to either setup.

The physical side of the interface is only part of the story. USB does not use traditional "start stop" signaling such as we were used to which had start bits, stop bits, parity bits and so on. The data on USB can be sent in several different ways, either packetized or streaming. If you want to take fullest advantage of USB, you must use a set of drivers which interact with the bus according to its protocol. However, with legacy equipment, and with the advent of USB-RS232 convertor chips that can hide all of the USB bus working from the user, it was realized that there might still be some life left in the old COM port idea from the IBM PC days. Many programs were written to use the COM port. A big example is GPS receivers. From the amateur point of view, radio interfaces to logging programs and for PC control are numerous. So the makers of the USB-serial chips provide drivers which allow the chip to show up as a "Virtual COM Port" or VCP. This uses USB to talk to the convertor, and a driver "maps" the chip as a COM port.  If you open Windows "Device Manager", it will show up as a COM port. This is shown below.

This shows that Windows mapped the device to COM9. Which COM number Windows comes up with is a little mysterious - it is not as predictable as when you set the jumpers on a serial card to tell it to use "COM3". In fact, it could come up with any number, depending on how many ports you have had connected in the past.  It is however, easy to change the COM number to something sensible - we recommend using COM1 - COM9, as the bootloader for the our amplifiers is restricted to these numbers. To change the port, double click on the COM9, and select the advanced properties:

You can then change the port number to anything you want from the drop-down menu. You can also clean up a couple of the defaults to improve performance. Set the latency timer to 1 msec, and de-select the "Serial Enumerator". You should then end up with something like this:

Here, I have switched the port to be COM8, and turned off the Serial Enumerator, and set the latency to 1. In the process, I received a prompt about the port number already being in use. This is one of the "wonders of Windows", since we saw before that there really is only one com port (9)- so it is unlikely that 8 is in use! So tell Windows to go ahead anyway. Windows seems to accumulate these "ghost" COM ports, and it is generally safe to ignore the warning. These ghost ports are what cause Windows to give strange numbers to a new USB-serial device that it has never seen before.

There is not much more than that to setting up your VCP using Windows. You should then be able to talk to the device from whatever program you are using by directing it to use the new COM port you just created. Conveniently, this only has to be done once, as there is a serial number in the USB-Serial chip that allows Windows to know that it has seen it before, and it will assign the same COM port number as when you set it up. So each time you plug USB into your PC from the device, you will get the same COM number.

73, Gordon, W0RUN 

It makes me pretty happy to see our staff whittling away at that sales backlog.  We've made good progress against all the production lines, thanks to a team effort here at the South Sunset facility.   

We have a great technical team here composed of Brad Focken, KØHM, Glenn Pladsen, AEØQ, Tom Walsh,W2CO, and Petar Pastar.  Yes, this is a very small team, and they are the guys who both work on repairs and also turn up the new amps that we ship out.  They work at their tech benches all day, juggling amps around, depending upon the priorities that I assign to each of them in our morning meetings.  When a new amplifier comes in to us, the technician assigned to that amp spends time calibrating and tuning it up, and then sends it into burn-in overnight.  The next day, the tech spends more time testing the amp until it is finally deemed ready to ship.

Repairs are interspersed with working on new equipment.   We frequently refer to an amp in for repair by the call sign of its owner, or the owner's name.  It is surprising how quick the turnover is, and an amp that was a hot topic one week, is only a faint memory the next. 

We continue to look forward to the new products in the pipeline and can't wait to have an expanded product line to offer. 

73, Kathy, KB2HDT 

Tell A Friend. 

It's worth $$'s for all Alpha owners, this is for you with our appreciation.

Through September 30 merely recommend one of the very best amplifiers on the market and receive a gift of appreciation from all of us at RF Concepts.

It is really simple. When your friend buys a new 8406, 8410 and/or 9500 Alpha Amplifier through your recommendation, and includes your name, address and call sign at the time the order is placed, you and your friend will each receive $150 from us as a form of our appreciation.

1)     The friend must have a separate address from the purchaser

2)     Naming your friend only applies at time of purchase and after full payment is made

3)     This offer only applies to the purchase of new amplifiers

4)     Offer ends 9/30/2011

It is my pleasure to announce Andrews Communications Systems, www.andrewscom.com.au as our new Australian reseller covering Australia, New Zealand and Asia. ACS is Australia's largest supplier of amateur radios, power supplies, linear amplifiers, scanners, antennas and optical equipment. They recently celebrated 35 years in business and they, along with Radioworld in Canada, are our only reseller and warranty service centers outside of the US.

Alpha Amplifiers are listed within their web site under linear products and appear first in the listing of manufacturers.

We wish Lee Andrews and his team the very best of success.

Some of you are aware of our generous trade in program. It is worth mentioning again. In all probability your older Alpha amplifier is worth more than you think. Now is as good a time as any to find out just how much you can receive when trading up to any of our current Alpha Amplifier models. Call Molly at 303-4739232 with questions and quotes.

Come visit with us at the Huntsville event the weekend of 8/20. Molly and Gordon will be present along with product demos and the latest from Alpha Amplifiers

As always, thank you for your continued support.

Mike Adell