Generating a chirp pulse, non-even transfers

[tom sutherland]

I want to generate a chirp signal. My idea was to have a sawtooth signal feed a 
VCO. The generated chirp repeats, so I was going to blank off the signal after 
the first chirp. I wanted to count the number of samples in the chirp with a 
python block and output the VCO chirp only when the blanking pulse was high. It 
sort of works but the python code doesn't count the regularly. It seems to 
count in random length blocks, so I get some "chirps output" that have 20 
chirps and some have 50, not the one chirp I want. I have attached my code.  
Thanks...Tom

My Python Block's Code:"""Embedded Python Blocks:
Each time this file is saved, GRC will instantiate the first class it findsto 
get ports and parameters of your block. The arguments to __init__  willbe the 
parameters. All of them are required to have default values!"""
import numpy as npfrom gnuradio import gr

class blk(gr.sync_block):  # other base classes are basic_block, decim_block, 
interp_block    """Embedded Python Block example - a simple multiply const"""
    def __init__(self, ONpulsecount=1000,OFFpulsecount=10000,threshold = 0.5):  
# only default arguments here        """arguments to this function show up as 
parameters in GRC"""        gr.sync_block.__init__(            self,            
name='pulseshaper',   # will show up in GRC            
in_sig=[np.complex64,np.float32],            out_sig=[np.complex64,np.float32]  
      )        # if an attribute with the same name as a parameter is found,    
    # a callback is registered (properties work, too).        self.ONpulsecount 
= ONpulsecount        self.OFFpulsecount = OFFpulsecount        self.threshold 
= threshold        self.count=0        self.pulseblanker = 1.0
    def work(self, input_items, output_items):        """example: multiply with 
constant"""           self.count = self.count + 1
        if self.count < self.ONpulsecount:            self.pulseblanker = 1.0   
     elif self.count < self.OFFpulsecount:            self.pulseblanker = 0.0   
     else:            self.count = 0    
        output_items[0][:] = input_items[0][:] * self.pulseblanker        
output_items[1][:] = self.pulseblanker                return 
len(output_items[0])

chirpGeneration.grc
Description: Binary data

chirpGeneration.py
Description: Binary data

chirpGeneration_epy_block_0.py
Description: Binary data