BACKGROUND The IQPro is a DDS VFO with dual outputs (I and Q) that tunes continuously from 0 to 30 MHz. It is designed to work with direct conversion receivers (such as the R2Pro) as well as multi-band transmitters. However, most people have been using the R2Pro in single or dual band rigs because the R2Pro needs different Low Noise Amplifiers (LNAs) for different frequency ranges. These LNAs provide a couple of functions. They amplify the input signals coming from the antenna before going to the receiver mixer and they provide reverse isolation so that the receiver doesn't send signals back out to the antenna. In addition to the need for band-specific LNAs, the multi-band transmitter also needs different Low Pass Filters (LPFs) for different frequency ranges to prevent harmonics from being transmitted. As the IQPro frequency changes to the different frequency ranges, it generates control signals which go to an output header. The intent was to provide a way to activate external circuitry to automatically switch to the correct LNA and LPF as the frequency changes. This LNA / LPF board does just that. WHAT IS IT? Gary Johnson, WB9JPS, and I have been working hard on the design and development of this multi-band LNA / LPF board to go along with the IQPro and R2Pro. Rick Campbell, KK7B, has been consulting with us along the way and he gave us a head start with some very important design ideas at the beginning of the project. He has reviewed the end result and has given the design his "thumbs up" approval. We are using Rick's basic R2Pro LNA design (as published in EMRFD) but we have a different LNA mute mechanism that was designed and prototyped by Gary. The project has been a lot harder than I originally thought it would be - and it's taken many design iterations to get where we are today. However, I think the result is outstanding! I'm really excited about it. I have posted the schematic, parts list (in Excel format) and a board snapshot (as shown in my PCB design program).in the "AA0ZZ-WB9JPS LNA-LPF Board" folder of this DDS-VFO group. It's also on my web site (www.cbjohns.com/aa0zz). Here's a general description of what we have developed and how it works. It may be helpful to look at the schematic and board picture as you read this. A basic PC board consists of a control section, an LNA section (containing 2 LNAs), a buffer-amplifier / pad, and an LPF section (containing 2 LPFs). There are "snap-off" break lines between the sections. To add two more LNAs and 2 LPFs to the basic board, the builder gets another board, "snaps" off the control section, installs the LNA and LPF components, and attaches the board "sandwich style" with corner spacers above the previous board. Up to three sandwich layers are possible. With the frequency scheme that I have in mind (see below), 6 LNAs and 5 LPFs are used to cover the 0 - 30 MHz range. There are "buses" at the edges the sections. This means that any single LNA and LPF can be engaged by attaching its input and output to the buses. Vertical wires are used to connect the various buses at the board edges. Two electronic switches (SPST) are used to engage the proper LNA (input and output) as the IQPro frequency changes and a MOSFET is used to control the mute for each LNA. Then, since the LPFs are designed to be attached to the output of the transmitter, it must handle more power than the LNA. For this reason, electronic switching could not be used for the LPFs so heavy-duty non-latching relays are used instead. (How much power can the relays handle? I'm not quite sure but it's much more than QRP power.) CONTROL SECTION: The control section has three "decoder" ICs in it. The 6 band-switch control signals coming from the IQPro are attached to the input header via a wiring harness and the signals are interpreted by three decoders. One is used to engage the appropriate LNA, one is used to mute all unused LNAs, and one is used to engage the appropriate LPF. A second input header in the control section brings the mute signal from the builder's T/R switch to the second decoder. The third decoder is a different type, since it must handle more power - to engage and hold the selected relay. (In this case, the device port is low-active and "sinks" the current from the LPF 12v source.) LNA SECTION: Two LNAs (with mutes) are on each board. Two Hittite HMC550 (SPST) switches are used for each LNA - one to connect the LNA to the input bus and one to connect it to the output bus. One control wire runs from the control section to each LNA to operate the two switches to engage the LNA. The Hittite switches were selected (by Gary) because of their outstanding low loss switching characteristics. They are non-latching, normally open switches.. By the way, the builder has great flexibility regarding which LNAs and LPFs he will put in the various "sandwich" layers. He just has to connect the appropriate control section wires to the corresponding LNA and/or LPF input pads. If the builder just wants a two bands, he can select them and connect the appropriate control section wires. Add two more bands later, etc. Easy and flexible. BUFFER-AMPLIFIER / PAD SECTION: One buffer-amplifier / pad is used for the entire project. It is always attached to the LNA output bus. The output of the buffer-amplifier / pad goes off-board to the receiver antenna input port. Note that the LNA output is being amplified and then padded back (by 6 dB) such that the receiver mixer always sees a 50 ohm drive. (Rick says the R2Pro will then "love it". Thanks to Rick and Wes Hayward, W7ZOI, for this basic buffer design and to Gary for his modifications.) LPF SECTION: The LPF section has input and output buses, since its input is taken from the output of the transmitter. If the builder wants to move the LPF "sandwich" to another location (i.e, near the transmitter) he just has to "snap off" all the LPF sections and move the LPF "sandwich". He will still have to run control wires, of course, but it's only one wire per band, plus ground and 12v power. FREQUENCY SCHEME: I have previously outlined the scheme that I was planning for this LNA/LPF project. Basically it's a change from what I originally planned for the IQPro because it got more complicated. I originally planned to have one IQPro output pin per band and expected the latching band relays to be driven directly from the band-switch header. However, as it turns out, there are more bands than originally planned because the LNAs and LPFs don't always switch in tandem as the frequency changes. This is the latest scheme with 10 frequency bands: # ---freq-------Ham Band------LNAFreq---------LNA#-------LPF# 1 0-1.8MHz ------(Below)------(none)---------(none)------ 1 2 1.8MHz-3.5MHz---160---------(none)---------(none)-------1 3 3.5MHz-7MHz------80---------3-4MHz-----------1----------2 4 7MHz-10.1MHz-----40---------6-8MHz-----------2----------3 5 10.1MHz-14MHz----30---------9-11MHz----------3----------3 6 14MHz-18Hz-------20--------13-15MHz----------4----------4 7 18MHz-21MHz------17--------18-22MHz----------5----------5 8 21MHz-24.9MHz----15--------18-22MHz----------5----------5 9 24.9MHz-28MHz----12--------24-30MHz----------6----------5 10 28MHz-30MHz-----10--------24-30MHz----------6----------5 This scheme uses the 6 LNAs designed by Rick for the R2Pro and it has and 5 LPFs, Implementing this scheme means new IQPro Driver PIC code is required. Now, three band-switch header pins will be used to specify the LNA and the other three will be used to specify the LPF. WHERE ARE WE RIGHT NOW Gary has prototyped the LNA / mute / amplifier / pad circuitry. Full prototype boards have been made and are currently being shipped to me from Texas. Gary and I will both be building and testing the prototypes. Until that time, we don't know exactly how close we are to the finish line. However, I'm really confident that we are VERY CLOSE! Gary is an "eagle eye" and has precluded a lot of useless and time consuming prototype board turns. We'll see how it works in a few days. WHAT ABOUT KIT AVAILABILITY? As I said, the project turned out to be lot more complicated than I originally envisioned. Consequently, the total parts cost is a lot higher than I hoped it would be. However, the performance was of utmost importance so we didn't skimp on anything to keep the cost down. The project uses ALMOST ALL SMD parts, but we've used the relatively large 1206 size to make them as easy as possible for home builders to handle. The control section has two SMT ICs (again relatively easy to handle) and one through-hole IC. (This IC isn't available in SMT format.) Four large T50 toroids are used in each LNA, two in each LPF, and one FT37-43 bifilar toroid is used in the buffer-amplifier. The relay (one per LPF) is through-hole. The through-hole LEDs in the control section are for debug purposes only and indicate which LNA and LPF is currently engaged. I've included a replacement for the Driver PIC of the IQPro in the parts list. This would be a drop-in replacement. What will a kit cost? I've discussed it with Bill Kelsey and we really haven't decided yet. It will probably be a low-volume kit. Who knows, maybe Gary and I will be the only ones to build them :-) Seriously, we will offer it as a kit if there is interest and it makes sense to everyone. As with the previous kits, the selling price will probably be not too far from the single-unit parts cost. Again, I wish it was cheaper but we couldn't do it without cutting corners. We wouldn't do that. These are the kit options that I expect we would offer::: 1) One base board with parts for the control section, two LNAs, buffer-amplifier, and 2 LPFs. New IQPro PIC also. 2) Two boards. Includes #1 above plus another board with with parts for 2 LNAs and 2 LPFs. (No control section or amplifier parts on second board.) 3) Full kit with 3 boards, parts for control section, buffer-amplifier, 6 LNAs and 5 LPFs, plus IQPro PIC. If this project is of interest to you, please let Bill Kelsey (N8ET@woh.rr.com) know. Or go to www.kangaus.com for links. Obviously no money is being exchanged (our policy!) so this is not an order but we would like to know what you are thinking. Obviously we will not start selling anything until we know that it works. However, we need to start planning - to see if it even makes sense to offer it as a kit and to get parts ordered if it does. In the mean time, go ahead and make your own "manhattan style" if you wish! Let me know how it works! Better yet, let us all know. Best Regards, -Craig, AA0ZZ