Member postings for Doubletop

Henry

A few to choose from here **LINK**

This is a good starting point. It was my first project

**LINK**

This is a good little engine, maybe something for #2

**LINK**

Pete

I was in the queue for the security check at Heathrow the other week, heading back to NZ. I started to turn out my pockets to put everything into my jacket pockets so it could go through the scanner. I then found I still had a set of keys for my mother’s house and on it was a small penknife. I was expecting a problem and took the penknife off the keyring and pointed out to the security guy that I had inadvertently kept the penknife with me. I fully expected it to go in the bin.

He gave it a cursory check and told me it wasn't a problem and handed it back to me. On the trip I was also going to be going through security in Singapore and Melbourne. I didn’t bother pointing it out and there weren’t any problems there either.

My wife had more of a problem with her cosmetics.

Pete

Bazyle

I steer clear of direct debit, not because I'm concerned about continuity, they are likely to charge you well before the renewal date. I am concerned about unnotified price hikes or, if notifications do occur, my complacency in checking them and doing something about it.

What I did like was the ability to pay for 3 years at a fixed and reduced rate. That option seems to have disappeared. Maybe as it removes the opportunity for 'proactive marketing'

Neil's on the case again so I'm sure it will be sorted. In the meantime, I’ll use the link at the top of this page.

Thanks Neil

Pete

Thanks Jason

The other point being that by using the link in the email it is not possible to change the option. Using the "subscribe" link above you can select either or both.

Michael

Good point; In this case it is ME but I do subscribe to ME and MEW

Pete

There is an element of déjà vu here as well. Last time I renewed  (3 years ago) there was a different price if you used the emailed link, the pricing in the renewal letter or the direct online 'subscribe" link. Neil was on the case back then.

Edited By Doubletop on 11/07/2018 11:00:09

Edited By Doubletop on 11/07/2018 11:08:45

Again - this is nothing to do with scam emails or dodgy email links. Let us please not loose the purpose of this thread.

Not a scam.

The link goes directly to the same url as you would get to if you followed the subscription link at the top of this page. It also has my correct account details.

No this is just an attempt to up the subscription by the third party subscriptions website.

Pete

I have just recieved and email from [email protected] advising me that I need to renew my subscription. In the email is a a link

"So what are you waiting for? "Simply click here to renew today"

This takes you to a renewal page that is for the print and digital copies. Currently I only subscribe to the print version. The link doesn't allow the type of subscription to be changed. Basically, they are trying to sucker me into buying both.

Just select the "Subscribe" link in the black bar above and take it from there. You'll be able to select which subscription you want.

Pete

Edited By Doubletop on 09/07/2018 22:01:59

Thanks Neil

Somewhere in the thread somebody had suggested the meteors would break up, which I wasn't too sure about but if it had been the case then ISS and meteor signals would be markedly different.

The thing I have been trying to reconcile is the faint diagonal lines in your plots that are changing frequency over time. The examples in Dr David Morgan doc don’t appear to have the same characteristics. He has the frequency shift (velocity) over a relatively short timeframe without the powerful ‘burst’ in the middle*. However, having spent years in a past life, peering at spectrum analyser displays of different types of radar signals I do know that the settings of the equipment can present a display that doesn't necessarily represent what you are looking for. Your setup and Dr Morgan’s could be looking at the same event and have different presentations. (* I’ve just realised Dr Morgans velocity display effectively ‘folds’ the inbound and outbound frequency shifts and combines them into one value of velocity)

When you say "pulses" I think you mean dwells. As you know Graves is a CW radar and the scan dwells for 3.2secs at a particular azimuth angle. A 45deg scan taking 19.2secs to complete. You could well miss a lot of events while it was dwelling on another sector.

As I say this is all academic for me as I can’t see the signals down here to be able to get some kit and join in the fun.

An interesting document

https://britastro.org/radio/projects/Detection_of_meteors_by_RADAR.pdf

Pete

Edited By Doubletop on 21/06/2018 06:34:02

Edited By Doubletop on 21/06/2018 06:34:40

Edited By Doubletop on 21/06/2018 06:35:00

Pointing Yagis - The Graves Radar has an elevation beam width of 25deg pitched up at 15deg. The latitude of Dijon is 47degN and by way of example Northampton is 53degN

If the Rx Yagi also had a beam width of 25deg then the pitch up should be around 13deg so 10deg would be OK as the elevation beam width would certainly be greater than 25deg as it needs to be 180deg in azimuth. There is something to be said for a better shape to the RX antenna polar diagram. Now if you were to have a 4 element array that stepped in sync with the Graves azimuth sweep....

ISS - The ISS plot is interesting as it has a greater doppler shift than the meteor returns. With such a strong return from a target that isn't breaking up on entry is interesting as it has similar characteristics to the meteor return that is allegedly breaking up.

The ISS return also has those faint spectral lines how are they explained? There are also the lines at 143,046,800 143,048,900 and 143,052,900 something in the receiver?

Like Dave this is becoming an interesting distraction, particularly as I have no chance whatsover of reciveing these signals from New Zealand.

Pete

Edited By Doubletop on 20/06/2018 21:40:56

Dave (SoD) got me looking at the spec for the Graves radar and the azimuth beam width is 7.5deg with 4 beams operating simultaneously and each beam doing 6 steps to provide 180deg coverage. Each step is 3.2 seconds. Looking at Neil’s plot the event is active for just under 3sec. Indicating that the duration of the event is a function of the time beam is illuminating the target, not necessarily the time the target is active.

Pete

Neil

Thanks; I'm getting to understand this so some degree, helped when I found I could zoom the image and read the detail.

Surely you can't use the total frequency shift as the indication of velocity as it represents closing and receding velocities? You can only use the deviation from the fundamental +ve and -ve

Alternatively could it be the case that the range of the crossing is so great that the closing velocity is relatively minimal and the bright cluster, on the fundamental, is really the main signal with minimal doppler shift. As your array has a wide beamwidth the cluster exits for all the time it is within your beamwidth. Indicated by the height of the cluster (Y). Then the frequency shifts being some sort of spectral noise or harmonics that exist for the duration of the event being at the same time as main cluster? Basically, for any point in time during the event there is a large return on the fundamental plus a secondary signal that sweeps +ve to -ve as the event progresses. It would be good to see a plot with an expanded (Y) axis.

In the case of the ISS, as it is so close, there would be doppler shift so it would also be interesting to see a plot of the ISS to see what the ISS spectrum looks like for comparison.

Pete

The main signal has a doppler shift of 900Hz and (using an online calculator) a velocity of ~950m/sec or 2125mph (towards Neils house)

Pete

( could well be wrong....)

Geoff

Thanks; a bit early in the day?

I get the concept of a waterfall display. So Y is time, with current time at the bottom and and X is frequency rising from left to right.

Pete

(edited  I've just realised I can zoom the image)

Edited By Doubletop on 20/06/2018 05:37:02

Neil

Can you describe what we are looking at here please?

I've been wondering what it is you are receiving. From what I’ve read here I guess it is the signal from the source being reflected of the ionisation trail. But what are you capturing? The reflected broadcast FM signal, the doppler shifted CW component or both?

As your last note suggests ‘slowing down’ so I guess you are getting the doppler shift in the X axis but is Y amplitude and the ‘big flash’ being the stronger reflected signal from the ionisation cloud? As I also guess the display is aggregated over time how is that represented?

If you are getting the doppler shifted signal can you determine the velocity of the vector in the axis towards the receiver?

Pete

For OPTUS D1 and Home and Away and Neighbours?

Pete

Start with the article by Artisan in ME 4470 Nov/Dec 2013 it provides the approach for setting up the axle weights. I then did an article in a recent ME on my weighbridge. Sorry I don't have the issue number to hand but no doubt somebody will be on to it pretty quickly.

As a result of the article Roger and I have been in touch which has resulted in the link provided by Dave.

http://modeleng.proboards.com/thread/12430/measuring-wheel-loading-on-locos

Pete

Edited By Doubletop on 22/05/2018 10:22:16

Paul

Try this as a starting point. Even if your unit isn't RCxcel the principles are much the same. (e.g. the units from Hobby King)

**LINK**

or

**LINK**

Pete

Werner

An excellent job.

You should expect the noise in the data, the engine itself introduces noise as a result of the reciprocating masses. It even happens with locos running on rails. Maybe some better fitting pins in the couplings could help a bit but don't try to do too much mechanical damping. Just do it in the processing of the raw data, as you have done.

Pete