Originally Posted by gandalf58
I have just been given this as an early Christmas present, I've managed to get it working well on VHF/UHF and now want to try HF. It had no instructions with it whatsoever but on the website it says to use HF you enter the desired frequency+50mhz
Can anyone advise me if this is correct?
Gandalf58, I am going to assume you are using SDR#. While SDR# is maybe not the best thing to run these radios it is pretty good and seems to be the most used, most supported, and most modified. I am also going to assume you have the software correctly installed and it is functioning the device.
First lets look at your Soft66RTL.
As with any of these RTL based receivers the frequency accuracy and stability is not going to be great. While on VHF and up this is not often too big an issue, in fact some do not even notice it, on HF it will tend to be much more noticeable. This is caused by two issues. Number one the upconverter itself introduces more frequency variation (the Ham-it-up is not quite as bad as the Soft66RTL upconverter, but still an issue), and number two the signals on HF are narrower banded and show the errors more quickly. Particularly when we start to look at SSB, CW, and digital signals. You should have the unit powered on and working for 20 minutes, allowing it to warm to operational temperature, before being too concerned about the frequency accuracy. I find mine drifts several kHz in the first 20 minutes of operation, and then stables out, at least as stable as it will get.
The upconverter and RTL combination is also going to have image and spur issues. Again this is less true with the external Ham-it-up but it is still a fact. The system will be very picky about gain levels.
I am not bad mouthing these setups, it is just a fact that these are the cheapest things you can use to get on HF and they show it in several aspects. I consider them a good value, but they can be frustrating if you expect Perseus or Excalibur level performance, both models costing more than 15 times what the Soft66RTL or a RTL Dongle plus Ham-it-up cost. If you expect a Rolls Royce for a Yugo price, you will be disappointed.
Notice there are two antenna connectors, one on each end of the unit. One is for the HF side (HF is technically below 30 MHz, but we will call the 3 to 50 MHz side the HF side). The other is for the VHF and up side (50 MHz and higher, actually about 25 MHz and higher). On the HF side of the device, the end with the HF antenna input, there is the mini USB port and an LED, also a small round hole, this hole is for adjusting the gain of the upconverter stage. On the other side, the VHF and up side, there is the VHF+ antenna input and a small slide switch.
To use the device you connect an HF antenna to the HF port, and a VHF and up antenna to the VHF+ port. VHF to the side with the switch, HF to the side with the LED.
To listen to HF you slide the switch on the side of the device to the “inside”, or towards the antenna port on that end of the unit. The LED on the far end should be green. To listen to VHF + you slide this switch to the “outside”, or away from the antenna port, and the LED goes red.
To use the Soft66RTL in VHF+ is pretty simple and after the switch is set to the proper position and the LED is red it is just like any other RTL dongle. There are a lot of instructions on how to use the normal RTLs on the web.
To use it in HF is a little different. You slide the switch to the inside, and make sure the LED is green. You then start the SDR# program like you normally would. However now all the frequencies will read 50 MHz too high. So you check mark the “Shift” box in the upper left corner and you enter –50000000 into the shift value. Notice the minus sign, you must make this a negative number.
This shift value does NOT change the frequency you are tuned to, but it does change the numbers that the software reports to you. Then you can simply tune to the HF frequency you want, say 5.000.000 (for 5 MHz), and away you go.
You will have to adjust the “Frequency Correction” (under the “Configure” button) to align the frequency on a known source, such as WWV or WWVH. You may find the Correction factor will not quite bring the frequency to true, and you may have to play with a combination of “Shift” values and the “Correction” values to get it right. Remember, on HF you really want the freq to be correct to inside 1 kHz, and preferably a good bit better than that. The unit must be up to operating temperature before youa ttempt this alignment, as I said before I allow the unit to be on for at least 20 minutes before doing this myself.
When you go back to VHF+ the “Shift” value will need to be removed, and you will quite probably have to re-align the frequency.
Hope that helps. Feel free to post any other questions or anything you need clarification on. If I have the answers I will be glad to help. Other people will probably have more information on SDR# itself, I do not use it much except when playinng with RTL dongles, and most of my SDRs are not RTL, so that is not often. I only own them and play with them so I have an idea of what other people are talking about. Also, I like to do comparisons so that I understand the relative performance of the models out there.