![]() There is a delay after Send goes high so this does not pose a problem when it comes to receiver protection.ģ. However for AM, FM, RTT or CW RF could be output very quickly. On SSB speech this would not be as much of a concern because of the natural operator delay in speaking after PTT is pressed. Typical switching time for relays is 5 to 15 ms. You can see that there is the possibility of RF being output within 3.6 milliseconds of Send going low. Here is a link to the TX timing on the 7200. The SDR software mutes the radio and puts in 30 to 60 dB of attenuation so that the AGC can recover quickly when PTT is released.Ģ. When you push the PTT button on the transceiver it will send a Tx command via CAT to Omni-Rig which forwards it to the SDR software. SDRUno and SDR-Console both have a mute function in the software that will operate if you have a CAT connection with the transceiver. This is long, but hope it can help someone.ġ. Should something unthinkable happen, those diodes will give a little bit of extra protection to the receiver. But if you do, just add it and keep the switching port.Īs extra-extra insurance, I put two 6amp diodes between the receive antenna port's center and ground. They both list for $79.95 and more my money, I got the normal model, as I don't need a jumper. The "SDR" model also nixes the regularly unused switching port that the normal model 1708 has. If you get the regular "1708" you can install the jumper yourself. There is a 3db loss in so doing, not a huge deal for receive. This is to allow the transceiver to "receive" even as the SDR is acting as a panadapter. The "SDR" model has a jumper that shorts the incoming from the transceiver to the antenna. There are two models, the 1708 and the 1708SDR I'll know in a day or two about the RSP2pro.Ī little insight to the MFJ-1708. This all has worked exceptionally well on the IC-R75. So we've got a bit of extra time delay on xmit, and a bit on recv too. So, just set the delay to something reasonable to assure the PTT is off, the radio has stopped transmitting, and your amp is off, before allowing the transfer of the antenna back to receive mode. No problem! The MFJ-1708 provides a 0-2 second time delay to switch back to "recieve mode". I've got enough time delay built in, to give it "insurance" upon pressing PTTīut wait. Relay #2 gets the radio into transmit mode. First it triggers the MFJ antenna switch, and also triggers relay #2. In operation, the mic triggers relay #1, which does two things. 01uF 600v, but that's because I had one handy! Any old ceramic or silver mica or polyfilm capacitor of similar value should do. My mic does not use the +8vDC supplied by the IC-7200, so I've got a capacitor to block the DC and allow the AC of the mic through. Its a bit of insurance, and cheap, and easy to do. the second relay is acting as a time delay, while the first relay triggers the MFJ-1708. That relay's NO contacts are used to key up the IC-7200. The remaining set of contacts on that relay energize the coil on the second relay. The NO contacts of the relay are wired to trigger the MFJ-1708. That line is routed inside the box the coil of one of the relays. I plug the ICOM mic into the "box" and tap into its PTT line. Inside the relay box are two 12vDC DPDT relays. There is also a 12v barrel jack ($1.50) on the box. I built up a short "jumper" to go from the box to the IC-7200, which used a bit of HeilWire and two ICOM mic plugs (maybe $10 total). There are input and output RCA jacks on the box (10 for $7.95 on Amazon). There are corresponding ICOM mic jacks on the box (about $6.00 each). What I did was build a small box with two relays in it. Instead of letting the IC-7200 key the MFJ-1708, I have completed a little relay box, to pre-trigger the MFJ-1708. So here's my simple work around, and remember - timing is everything. I've been thinking about the RSP2pro and its lack of a mute function. That, along with the MFJ-1708 has given great results, but. Basically, it shuts off the +5vDC power going to the front end. Timing is everything, and the IC-R75 has a "mute" function with kills the front end of the radio. Results have been ok using the MFJ-1708 antenna switch. I've been playing with a receiver, an ICOM IC-75, sharing the same antenna as the IC-7200. The rig is an ICOM IC-7200 and AL-811 amp. That hasn't changed.īut I also want to use it as a panadapter for my HF rig. ![]() In another thread, I explained how I'm wanting to use the RSP2pro as a diagnostic tool for signal strength evaluation. ![]() Consider this still a bit "experimental" but I think I'm on the road to success, and thought I'd share
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |