Forum Replies Created
August 19, 2017 at 8:14 am #1529
February 16, 2017 at 7:13 am #1446
The Flex has now also sold.
January 30, 2017 at 7:11 am #1438
The amp is sold
January 29, 2017 at 6:40 pm #1437
I posted these on QRZ.com The GARA prices above still apply, if anyone local wants to buy these!
March 22, 2016 at 11:28 am #1253
This is pretty cool! I didn’t know about this. Thanks for sharing with us. I’m definitely going to be checking it out.
December 7, 2015 at 8:17 am #1080
I’d say both of these duplexers are useable, they’d both do the job acceptably. Remember that the Diamond was broken, after just a few weeks in service I had to take it out of service because of broken solder joints. I had to repair those solder joints in order to do these tests.
Even though both of these are useable there is a clear winner here based on these tests. The MFJ-916B basically mopped the floor with the diamond competition with 20dB Better reject. Not to mention the much cleaner looking, sharper filters. The filters appear to have actually been tuned instead of just slapped together and accepted as “good enough”
I had a lot of fun doing this testing, and now, I’ll put this MFJ duplexer into service on my new antenna knowing that it’s going to do a good job for me keeping my UHF Dstar Hotspot and my 2m radio from causing problems with each other.
Let me know if you have any suggestions for further testing methods, or if you have any questions. If anyone here has anything they’d like to test, let me know, I have a lot of fun doing this type of stuff.
This time Mississippi’s Finest Junk beats Diamond’s hands down.
December 7, 2015 at 8:08 am #1079
The next thing I wanted to check out is the actual out of band attenuation of each. For this I used an S12 test on a network analyzer. Unfortunately this network analyzer only goes up to 200Mhz so I can only test reject on the UHF side by sweeping RF in the 2m band through the UHF side of the duplexer. First up is the reject on the diamond MX-72:
What you see here is the amount of VHF signal that is passing through the UHF side of the duplexer, the attenuation is around -46dB Not bad really, that’s passable. I also checked the insertion loss, which turned out to be less than 1dB, around 0.8dB, which is pretty darn good.
Now let’s have a look at that MFJ-916B:
65 dB of attenuation! That’s almost a full 20dB better! Wow, now that’s a BIG improvement.
Insertion loss is almost exactly the same between the two at about 0.8dB less than 1dB insertion loss.
December 7, 2015 at 7:50 am #1078
Here is the same sweep test through the MFJ-916B
Now that’s refreshing, this filter gets it’s job done in less than half the bandwidth of the Diamond one. 3dB rolloff is around 220Mhz, looks nice and sharp.
3dB rolloff around 311 Mhz
Hot DOG! At this point I get somewhat excited, it’s going to be really nice looking when I overlap the two filter sweeps. Check it out.
December 7, 2015 at 7:37 am #1077
The first thing I did with these was to use a signal generator and spectrum analyzer to sweep through the filters and with max-hold record the amplitude of the signal to make it through each of the filters. That’s basically all these things really are, a Low pass filter that the 2m side passes through and a High Pass filter designed for the UHF side to pass while rejecting the VHF signals.
Here is what the sweep of the Diamonds LPF(low pass filter) looks like:
This is a 200Mhz wide sweep centered on 250Mhz, the filter in the diamond starts rolling off around 190Mhz and doesn’t really reach full attenuation until almost 350Mhz. Not a very sharp Filter at all.
And the HPF from the Diamond:
A little bit Sharper but still a nice lazy roll down to full attenuation.
If you overlapped these two filters traces you’d just see a flat line across the sweep. I was sweeping with a -50dBm signal from 150Mhz to 350Mhz:
- This reply was modified 2 years, 3 months ago by Cameron Conover.
October 20, 2015 at 7:00 am #1027
I would like to do a club meeting program where we test spurious emissions on people’s HT’s. I think it would be a lot of fun and everyone can learn a few things. I’m working on the details for that.
You can find the procedures for a spectral purity test here:
July 30, 2015 at 6:29 am #911
Well, I think I changed my mind, I really enjoyed having it during 13 colonies. LOL, I think I’m going to hang onto it. Sorry. .
June 5, 2015 at 11:17 pm #832
I added a couple things to the supplies and equipment spreadsheet.
Caution tape, if anyone has a roll of caution tape we could sure use it.
Also some stakes like a tomato stake type deal that we can use to hold up the caution tape around certain areas.
May 27, 2015 at 3:37 pm #819
Field Day planning meeting tonight, 7pm, at Tannenbaum Park. Please park on Green Acres Ln, the gates to the park will be closed but we can park on the road.
I have about 6 confirmations for Field Day meal attendance. That is not enough to warrant the effort to prepare any special meals. Please, Please, if you are interested in enjoying a nice meal at the field day, please email me so that I can get an idea of how many will be coming. email@example.com
See y’all tonight.
May 1, 2015 at 9:33 am #782
W4GSO Field Day Supplies and Equipment list:
W4GSO Field Day committee Contact Form:
FIeld Day Operators Schedule:(look for the Tabs at the bottom of the spreadsheet to select which station you are signing up for CW, Digital, SSB)
- This reply was modified 2 years, 10 months ago by Cameron Conover.
April 30, 2015 at 7:59 am #777
Thank you to everyone who showed up last night to the Field Day planning meeting. I did get the room reserved for two more meetings. May 13th and May 27th same time and place.
I will be putting together some Google Docs spreadsheets that we can all edit and update to keep track of what we have and what we need. Probably tomorrow, since I have a busy day today.
Also, I think we could use google docs spreadsheets for Station sign ups, if the band captains want to do that. It worked well for W1AW/4
Thank you, again! it was great to see everyone last night.