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   Home   Help Search  
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 41 
 on: Yesterday at 05:57:00 PM 
Started by KA1VF - Last post by KA1VF
   My "MOS" (Military Occupational Specialty) in the U.S. Navy was "RM" (Radioman),
   and I remember that during a orientation/training they briefly mentioned that any
   CW operation on Military freq's ("Circuits") should be limited to the 25 wpm max.

   Regarding CW operation on Commercial freq's (i.e. Maritime), I've never seen any
   written regulations regarding the 25 wpm max. But, it must have been at least a
   "Gentleman's" agreement because most/all Shore stations and Ship stations seem
   to have adhered to it.

   If you want to research this CW speed topic further, I'd suggest that you peruse
   the following website www.radiotelegraphy.net/ and click on the top left screen
   that is titled "Maritime Radio History".

 42 
 on: Yesterday at 05:50:09 PM 
Started by KG7A - Last post by VK6HP
Steve, you might have missed the earlier dialogue re searching for the best height .  My loop is only about 1 loop diameter above ground, and the PVC mast section is only about 0.5m long, the associated rotator being attached to a galvanized water pipe of similar length above ground..  Mast/loop attachments are via PVC plumbing fittings.  Even with Perth gales, there's no issue.

73, Peter.

 43 
 on: Yesterday at 05:44:11 PM 
Started by NN2X - Last post by NN2X
Hi Fellow Ham operators

I don't know if this is the place to ask this questioned, but I will ask anyway!

ICOM has a comparison with the ICOM 7610 with ICOM 7600, 7300, 7851 (Graphically) but not the ICOM 7700

Here is the URL..Scroll down and you will see the graph comparison (RMDR Specs) /Reciprocal mixing dynamic range

http://www.ab4oj.com/icom/ic7610/main.html

However, you will not see a comparison with ICOM 7610 ( $ 3,900) and the ICOM 7700 (5,900).

I am just wondering if the ICOM 7610 is a better rig than ICOM 7700. If that is the case (ICOM 7610) is better, but cost less, maybe that is why their is no comparison chart (RMDR).

Has anyone else noticed this..?

 

 44 
 on: Yesterday at 05:34:20 PM 
Started by KE8ICK - Last post by K6AER
In the cell phone industry we used a single deep ground rod for surge grounding on cell towers. Typically these would be up to 40 feet deep with ground resistance well under 2 ohms. Most lightning RF energy (98 %) is under 100 Khz. This was measured with a HP vector spectrum analyzer. The sphere of influence can be 8 times greater with a 40 foot ground rod than 20 ten foot rods spaced in a radial pattern.

 45 
 on: Yesterday at 05:30:27 PM 
Started by N4EDI - Last post by AA4PB
I was going to say the same about the return wire (pin 1). This wire likely ends up being in parallel with the coax cables as the wire is connected to the rotor case and to the control box safety ground on the power plug. If the wire is too small of a gauge or has a poor connection then you may have excessive AC current flowing in the coax shields. Does the position indicator needle jump or flutter when you press the brake release? The position pot center arm also returns via pin 1.
 

 46 
 on: Yesterday at 05:23:00 PM 
Started by N4EDI - Last post by WB4SPT
perhaps the ground return from the rotator is open.   The rotator uses 30V ac, and the return shows grounded to the case.  So, if the current is not going down the correct return wire, it may then return via the coax shields, etc. 

 47 
 on: Yesterday at 05:21:05 PM 
Started by GM4CUX - Last post by K6AER
You can replace the 811A's with the higher dissipation 572B's. The power out will be the same (power supply limitations) but make sure the tubes are from the same batch lot and date. Best to buy the tubes from a known source with a warranty. RF Parts has served me well in the past.

 48 
 on: Yesterday at 05:20:06 PM 
Started by 9A5BDP - Last post by W1VT
http://qrznow.com/the-vhfuhf-dx-book-2017-replica-edition-is-now-available-for-free-download/

This book has detailed information on building and operating the K2RIW amplifier.

 49 
 on: Yesterday at 05:14:01 PM 
Started by KB1SNJ - Last post by WB6BYU
Quote from: KB1SNJ

...I had to remove 7 feet (down to 123ft, inverted VEE) to get the best SWR at the higher end of the 80M band. The 40M band still seemed ok but 20M was now WAY out the top at around 15mHz.



That's typical.  Operation depends on having a high impedance at the feedpoint because the wire is
an integer multiple of 1/2 wavelength.  That's great for 3.5 MHz, which gives you 7 and 14 MHz, but
when you shorten it to tune to 3.95 MHz then your harmonic resonances are 7.9 and 15.8 MHz.

One suggestion that I've seen is to keep the wire the original length, but insert a 470pf capacitor
(or somewhere around there) in the middle of the wire:  that moves the 80m resonance with little
effect to the even multiples.  (Might make 30m worse though.)

Installing the antenna as an inverted vee, especially with a sharp angle, will shift the resonance somewhat,
and not necessarily by similar amounts on each band.  So it isn't unexpected that they don't line up
exactly.



Quote

Also, the 10M band never was even close to operable.



Given what you measured using the transformer with a 3300 ohm load, this isn't surprising.
10m had a low impedance with high reactance.

How long is the coax between your analyzer and the balun when you were testing it?

My guess is that the winding length may be too long for 10m, or a similar problem.
Or try SV1IYF's approach and add another ~113 pF to the capacitor.

Making such a transformer that covers a very wide frequency range with a high turns
ratio is not a trivial exercise.





 50 
 on: Yesterday at 05:13:09 PM 
Started by KD8MJR - Last post by K0UA
By the way for those that think you have to "go into some horrible menu" to change RF power, you are wrong.  To change RF power simply punch the multi knob in the nose. Twist the knob to adjust the power, and when done, punch the multi knob in the nose.  It all takes about 1/2 of a second. No horrible menus.  Same for keying speed in CW mode except after punching the multi knob in the nose press the cw speed icon if it was left on power and quickly adjust cw keying speed.  Then punch multi knob.  The system is far easier to operate and give far better control and readout than the independent knobs on my 756 pro 3.  The touch screen revolution is far better, far more efficient and far more precise.

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