630 meter swr question ...

Gary L. Robinson

Probably a dumb question but - will most hf swr bridges work somewhat accurately on 630 meters and class D amplifiers?

I am really looking forward to playing around on digital chats on 630 meters assuming I am OK'd by the powers that be through the plc database thingee I just filled out yesterday.  And of course when my 6400 shows up hihi

Steven WA8Y

Yes, me too. Filled out the form over a month ago when the website was posted by the ARRL. Still waiting to hear if I have clearance.

WA2SQQ

I think I heard someone saying, "if you don't hear from them, you are OK"

Andrew VK5CV

http://www.giangrandi.ch/electronics/lw-swr/lw-swr.shtml
This one works well to get close to the correct impedance.
I use an auto transformer to match from 50ohm feed to about 25ohms.
In the shack I use a scope match.
http://ve7sl.blogspot.com.au/2014/08/your-lf-stations-best-friend-scopematch.html
Some SWR meters will work, give it a try.
My LDG Z100 tunes on 630m.
At the antenna I use a current meter or a simple field strength meter for fine tuning.
For more serious work the Tecsun PL365 (CountryCom GP5) or PL360 have a very linear field strength meter in dBuV for far field measurements. 
VK5AI and I have measured the antenna factor of the accessory external loopstick that it comes with at 20dBuV/m at 475kHz so add that to the measurement. The internal antenna is about 40dBuV/m.
Andrew VK5CV

HCampbell WB4IVF

The Telepost LP100A manual shows several couplers that cover 630M.  They may be special order though.

Howard

Gary L. Robinson

This is off of the ARRL site (the first paragraph).  The last sentence says precisely what you heard.

The link to the complete article : http://www.arrl.org/news/fcc-opens-630-and-2200-meter-bands-stations-must-notify-utc-before-operatin...

09/15/2017

The FCC has announced that the Office of Management and Budget has approved, for 3 years, the information-collection requirement of the Commission’s March 29 Report and Order (R&O) that spelled out Amateur Radio service rules for the two new bands — 630 meters and 2200 meters. Notice of the action appears in today’s edition of the Federal Register. Before using either band, stations must notify the Utilities Technology Council (UTC), formerly the Utilities Telecom Council, that they plan to do so, and if UTC does not respond within 30 days, they may commence operation.

Gary L. Robinson

Thanks Andrew!  That tells me several ways to approach the SWR question. 

I am really excited and interested in running Olivia (narrow band configurations) and related digital modes and will be working on antennas + amplifier this coming spring.

Ned K1NJ

      I'll bet that someone could take apart an old Heathkit SWR meter, do a few mods, add
a FET or two maybe, and a battery.  Might get meaningful SWR out of it.  Maybe not good
power readings as would the LP product, but SWR nevertheless.

                     Ned,  K1NJ

                          

John AE5X

I'd suggest an antenna analyzer such as the FA-VA4. It will tell you what you need to know to operate and will help you get a 630m antenna built with a proper loading coil.

Many 630m ops are also using a ScopeMatch:
http://ve7sl.blogspot.com/2014/08/your-lf-stations-best-friend-scopematch_5.html

I used my F6300 last night on 630m WSPR with a G0MRF 300W amp kit running 40 watts (2 watts ERP) and the combo performed splendidly. Details on my blog for whoever's interested.

John AE5X
https://ae5x.blogspot.com/

HCampbell WB4IVF

Recent posts on the LP500 Yahoo group below.  Looks like the LP500/700 and LP100 should be fine on 630M using the stock HF couplers.

Howard

-------------------

Larry,

Do you have any data on the usability / accuracy of the LP-500 and LPC-501 coupler on 630M (475kHz+-)? Likewise for the LP-100 and LPC1 coupler on 630M?  Several of us with these meters are constructing amps for 630M and would like to have a usable watt meter.
---
Chuck, AE4CW

 

Yes. I have tested LPC501 down to 450 kHz, and it was accurate for both power and SWR. Measured insertion loss was 0.01 dB. These tests were at 10W output from an instrumentation amplifier, so I don't know about power handling, but I would guess it would be no problem unless the antenna is a piece of wet spaghetti ;-)

I checked an LPC1 and it was down 0.085 dB at 465 kHz, which is roughly 2%. The measured return loss at 475 kHz was 33 dB, and insertion loss was 0.08 dB. The insertion loss is higher on the LPC501 because it uses a transformer across the load to measure voltage, and the transformer has shunt inductive reactance, of course. The LPC501 uses a capacitive divider. I should point out that we have a number of special couplers available for LP-100A for frequencies down to 40 kHz. These are normally used for industrial applications.

Larry N8LP